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	$144.90	4.526%	$151.4582	$151.46	$151.45	$151.50
Purchase #2	$175.85	11.380%	$195.8617	$195.86	$195.85	$195.90
Purchase #3	$170.69	10.648%	$188.8651	$188.87	$188.85	$188.90
Purchase #4	$185.25	3.181%	$191.1428	$191.14	$191.15	$191.10
Purchase #5	$26.89	11.106%	$29.8764	$29.88	$29.90	$29.90
Purchase #6	$148.94	11.268%	$165.7226	$165.72	$165.70	$165.70
Purchase #7	$53.77	8.800%	$58.5018	$58.50	$58.50	$58.50
7 purchase totals =	$906.29		$981.4286	$981.43	$981.40	$981.50