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	$93.90	5.759%	$99.3077	$99.31	$99.30	$99.30
Purchase #2	$146.70	3.637%	$152.0355	$152.04	$152.05	$152.00
Purchase #3	$39.69	10.418%	$43.8249	$43.82	$43.80	$43.80
Purchase #4	$174.69	8.222%	$189.053	$189.05	$189.05	$189.10
Purchase #5	$68.53	11.125%	$76.154	$76.15	$76.15	$76.20
Purchase #6	$137.99	9.413%	$150.979	$150.98	$151.00	$151.00
Purchase #7	$200.88	6.618%	$214.1742	$214.17	$214.15	$214.20
7 purchase totals =	$862.38		$925.5283	$925.52	$925.50	$925.60