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	$155.28	13.307%	$175.9431	$175.94	$175.95	$175.90
Purchase #2	$29.27	7.438%	$31.4471	$31.45	$31.45	$31.40
Purchase #3	$30.59	7.374%	$32.8457	$32.85	$32.85	$32.80
Purchase #4	$45.58	12.197%	$51.1394	$51.14	$51.15	$51.10
Purchase #5	$237.79	11.235%	$264.5057	$264.51	$264.50	$264.50
Purchase #6	$235.45	10.115%	$259.2658	$259.27	$259.25	$259.30
Purchase #7	$112.69	11.203%	$125.3147	$125.31	$125.30	$125.30
7 purchase totals =	$846.65		$940.4615	$940.47	$940.45	$940.30