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	$75.49	8.869%	$82.1852	$82.19	$82.20	$82.20
Purchase #2	$10.36	4.477%	$10.8238	$10.82	$10.80	$10.80
Purchase #3	$55.76	11.155%	$61.98	$61.98	$62.00	$62.00
Purchase #4	$14.85	9.105%	$16.2021	$16.20	$16.20	$16.20
Purchase #5	$186.33	6.861%	$199.1141	$199.11	$199.10	$199.10
Purchase #6	$182.90	7.415%	$196.462	$196.46	$196.45	$196.50
Purchase #7	$50.73	3.592%	$52.5522	$52.55	$52.55	$52.60
7 purchase totals =	$576.42		$619.3194	$619.31	$619.30	$619.40