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	$190.48	4.216%	$198.5106	$198.51	$198.50	$198.50
Purchase #2	$204.72	9.369%	$223.9002	$223.90	$223.90	$223.90
Purchase #3	$113.54	12.605%	$127.8517	$127.85	$127.85	$127.90
Purchase #4	$122.85	8.386%	$133.1522	$133.15	$133.15	$133.20
Purchase #5	$126.63	3.655%	$131.2583	$131.26	$131.25	$131.30
Purchase #6	$234.49	10.283%	$258.6026	$258.60	$258.60	$258.60
Purchase #7	$37.89	7.616%	$40.7757	$40.78	$40.80	$40.80
7 purchase totals =	$1,030.60		$1,114.0513	$1,114.05	$1,114.05	$1,114.20