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	$114.83	9.106%	$125.2864	$125.29	$125.30	$125.30
Purchase #2	$74.37	12.801%	$83.8901	$83.89	$83.90	$83.90
Purchase #3	$146.76	3.454%	$151.8291	$151.83	$151.85	$151.80
Purchase #4	$107.52	3.404%	$111.18	$111.18	$111.20	$111.20
Purchase #5	$184.29	6.117%	$195.563	$195.56	$195.55	$195.60
Purchase #6	$18.38	11.519%	$20.4972	$20.50	$20.50	$20.50
Purchase #7	$146.25	9.629%	$160.3324	$160.33	$160.35	$160.30
7 purchase totals =	$792.40		$848.5782	$848.58	$848.65	$848.60