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	$135.46	12.453%	$152.3288	$152.33	$152.35	$152.30
Purchase #2	$40.62	13.231%	$45.9944	$45.99	$46.00	$46.00
Purchase #3	$67.83	6.554%	$72.2756	$72.28	$72.30	$72.30
Purchase #4	$96.84	10.398%	$106.9094	$106.91	$106.90	$106.90
Purchase #5	$41.67	6.208%	$44.2569	$44.26	$44.25	$44.30
Purchase #6	$76.53	7.362%	$82.1641	$82.16	$82.15	$82.20
Purchase #7	$114.46	10.326%	$126.2791	$126.28	$126.30	$126.30
7 purchase totals =	$573.41		$630.2083	$630.21	$630.25	$630.30