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	$89.33	11.479%	$99.5842	$99.58	$99.60	$99.60
Purchase #2	$68.76	4.222%	$71.663	$71.66	$71.65	$71.70
Purchase #3	$64.72	11.291%	$72.0275	$72.03	$72.05	$72.00
Purchase #4	$138.43	5.555%	$146.1198	$146.12	$146.10	$146.10
Purchase #5	$219.38	9.529%	$240.2847	$240.28	$240.30	$240.30
Purchase #6	$48.26	12.491%	$54.2882	$54.29	$54.30	$54.30
Purchase #7	$250.42	5.803%	$264.9519	$264.95	$264.95	$265.00
7 purchase totals =	$879.30		$948.9193	$948.91	$948.95	$949.00