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	$132.46	13.288%	$150.0613	$150.06	$150.05	$150.10
Purchase #2	$155.96	10.550%	$172.4138	$172.41	$172.40	$172.40
Purchase #3	$54.73	6.357%	$58.2092	$58.21	$58.20	$58.20
Purchase #4	$66.64	7.353%	$71.54	$71.54	$71.55	$71.50
Purchase #5	$190.92	7.198%	$204.6624	$204.66	$204.65	$204.70
Purchase #6	$105.85	6.294%	$112.5122	$112.51	$112.50	$112.50
Purchase #7	$13.56	10.176%	$14.9399	$14.94	$14.95	$14.90
7 purchase totals =	$720.12		$784.3388	$784.33	$784.30	$784.30