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	$146.64	3.182%	$151.3061	$151.31	$151.30	$151.30
Purchase #2	$243.41	5.142%	$255.9261	$255.93	$255.95	$255.90
Purchase #3	$180.65	3.471%	$186.9204	$186.92	$186.90	$186.90
Purchase #4	$139.98	3.363%	$144.6875	$144.69	$144.70	$144.70
Purchase #5	$223.67	11.559%	$249.524	$249.52	$249.50	$249.50
Purchase #6	$7.84	4.466%	$8.1901	$8.19	$8.20	$8.20
Purchase #7	$103.81	12.574%	$116.8631	$116.86	$116.85	$116.90
7 purchase totals =	$1,046.00		$1,113.4173	$1,113.42	$1,113.40	$1,113.40