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	$95.43	3.284%	$98.5639	$98.56	$98.55	$98.60
Purchase #2	$85.81	11.676%	$95.8292	$95.83	$95.85	$95.80
Purchase #3	$100.59	10.651%	$111.3038	$111.30	$111.30	$111.30
Purchase #4	$99.98	13.198%	$113.1754	$113.18	$113.20	$113.20
Purchase #5	$35.65	9.666%	$39.0959	$39.10	$39.10	$39.10
Purchase #6	$214.51	4.576%	$224.326	$224.33	$224.35	$224.30
Purchase #7	$195.84	8.823%	$213.119	$213.12	$213.10	$213.10
7 purchase totals =	$827.81		$895.4132	$895.42	$895.45	$895.40