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	$81.77	13.173%	$92.5416	$92.54	$92.55	$92.50
Purchase #2	$92.27	3.422%	$95.4275	$95.43	$95.45	$95.40
Purchase #3	$236.93	3.620%	$245.5069	$245.51	$245.50	$245.50
Purchase #4	$173.72	10.494%	$191.9502	$191.95	$191.95	$192.00
Purchase #5	$81.30	4.223%	$84.7333	$84.73	$84.75	$84.70
Purchase #6	$7.89	10.518%	$8.7199	$8.72	$8.70	$8.70
Purchase #7	$54.28	9.754%	$59.5745	$59.57	$59.55	$59.60
7 purchase totals =	$728.16		$778.4539	$778.45	$778.45	$778.40