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	$196.39	7.325%	$210.7756	$210.78	$210.80	$210.80
Purchase #2	$64.35	10.407%	$71.0469	$71.05	$71.05	$71.00
Purchase #3	$81.98	9.281%	$89.5886	$89.59	$89.60	$89.60
Purchase #4	$40.57	6.275%	$43.1158	$43.12	$43.10	$43.10
Purchase #5	$112.87	11.276%	$125.5972	$125.60	$125.60	$125.60
Purchase #6	$225.98	13.270%	$255.9675	$255.97	$255.95	$256.00
Purchase #7	$18.38	6.121%	$19.505	$19.51	$19.50	$19.50
7 purchase totals =	$740.52		$815.5966	$815.62	$815.60	$815.60