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	$124.87	5.591%	$131.8515	$131.85	$131.85	$131.90
Purchase #2	$93.52	13.143%	$105.8113	$105.81	$105.80	$105.80
Purchase #3	$93.32	13.549%	$105.9639	$105.96	$105.95	$106.00
Purchase #4	$240.43	5.806%	$254.3894	$254.39	$254.40	$254.40
Purchase #5	$234.70	8.152%	$253.8327	$253.83	$253.85	$253.80
Purchase #6	$83.64	12.606%	$94.1837	$94.18	$94.20	$94.20
Purchase #7	$162.32	11.170%	$180.4511	$180.45	$180.45	$180.50
7 purchase totals =	$1,032.80		$1,126.4836	$1,126.47	$1,126.50	$1,126.60