Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$180.79	11.378%	$201.3603	$201.36	$201.35	$201.40
Purchase #2	$162.46	13.451%	$184.3125	$184.31	$184.30	$184.30
Purchase #3	$106.73	4.374%	$111.3984	$111.40	$111.40	$111.40
Purchase #4	$171.58	4.714%	$179.6683	$179.67	$179.65	$179.70
Purchase #5	$151.33	13.228%	$171.3479	$171.35	$171.35	$171.30
Purchase #6	$146.55	6.573%	$156.1827	$156.18	$156.20	$156.20
Purchase #7	$152.81	4.815%	$160.1678	$160.17	$160.15	$160.20
7 purchase totals =	$1,072.25		$1,164.4379	$1,164.44	$1,164.40	$1,164.50