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	$38.55	7.668%	$41.506	$41.51	$41.50	$41.50
Purchase #2	$13.86	12.112%	$15.5387	$15.54	$15.55	$15.50
Purchase #3	$24.72	9.820%	$27.1475	$27.15	$27.15	$27.10
Purchase #4	$46.58	6.602%	$49.6552	$49.66	$49.65	$49.70
Purchase #5	$96.75	3.587%	$100.2204	$100.22	$100.20	$100.20
Purchase #6	$75.37	3.398%	$77.9311	$77.93	$77.95	$77.90
Purchase #7	$247.50	3.148%	$255.2913	$255.29	$255.30	$255.30
7 purchase totals =	$543.33		$567.2902	$567.30	$567.30	$567.20