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	$137.78	7.338%	$147.8903	$147.89	$147.90	$147.90
Purchase #2	$186.63	5.375%	$196.6614	$196.66	$196.65	$196.70
Purchase #3	$55.38	7.539%	$59.5551	$59.56	$59.55	$59.60
Purchase #4	$148.70	10.404%	$164.1707	$164.17	$164.15	$164.20
Purchase #5	$106.73	5.315%	$112.4027	$112.40	$112.40	$112.40
Purchase #6	$172.81	6.257%	$183.6227	$183.62	$183.60	$183.60
Purchase #7	$222.27	10.118%	$244.7593	$244.76	$244.75	$244.80
7 purchase totals =	$1,030.30		$1,109.0622	$1,109.06	$1,109.00	$1,109.20