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	$40.32	3.480%	$41.7231	$41.72	$41.70	$41.70
Purchase #2	$176.63	3.568%	$182.9322	$182.93	$182.95	$182.90
Purchase #3	$10.70	6.230%	$11.3666	$11.37	$11.35	$11.40
Purchase #4	$31.69	5.702%	$33.497	$33.50	$33.50	$33.50
Purchase #5	$95.39	11.615%	$106.4695	$106.47	$106.45	$106.50
Purchase #6	$61.95	9.113%	$67.5955	$67.60	$67.60	$67.60
Purchase #7	$55.98	9.289%	$61.18	$61.18	$61.20	$61.20
7 purchase totals =	$472.66		$504.7639	$504.77	$504.75	$504.80