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	$201.89	12.484%	$227.0939	$227.09	$227.10	$227.10
Purchase #2	$14.73	7.761%	$15.8732	$15.87	$15.85	$15.90
Purchase #3	$58.32	7.743%	$62.8357	$62.84	$62.85	$62.80
Purchase #4	$93.92	7.420%	$100.8889	$100.89	$100.90	$100.90
Purchase #5	$240.58	4.385%	$251.1294	$251.13	$251.15	$251.10
Purchase #6	$209.75	6.144%	$222.637	$222.64	$222.65	$222.60
Purchase #7	$129.95	8.851%	$141.4519	$141.45	$141.45	$141.50
7 purchase totals =	$949.14		$1,021.9100	$1,021.91	$1,021.95	$1,021.90