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	$198.57	12.384%	$223.1609	$223.16	$223.15	$223.20
Purchase #2	$176.93	11.612%	$197.4751	$197.48	$197.50	$197.50
Purchase #3	$88.77	11.650%	$99.1117	$99.11	$99.10	$99.10
Purchase #4	$223.71	10.519%	$247.2421	$247.24	$247.25	$247.20
Purchase #5	$66.49	7.281%	$71.3311	$71.33	$71.35	$71.30
Purchase #6	$43.65	7.632%	$46.9814	$46.98	$47.00	$47.00
Purchase #7	$79.98	13.478%	$90.7597	$90.76	$90.75	$90.80
7 purchase totals =	$878.10		$976.0620	$976.06	$976.10	$976.10