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	$100.42	5.297%	$105.7392	$105.74	$105.75	$105.70
Purchase #2	$91.43	7.419%	$98.2132	$98.21	$98.20	$98.20
Purchase #3	$239.45	10.560%	$264.7359	$264.74	$264.75	$264.70
Purchase #4	$24.72	10.409%	$27.2931	$27.29	$27.30	$27.30
Purchase #5	$91.32	13.773%	$103.8975	$103.90	$103.90	$103.90
Purchase #6	$156.30	6.631%	$166.6643	$166.66	$166.65	$166.70
Purchase #7	$225.96	11.165%	$251.1884	$251.19	$251.20	$251.20
7 purchase totals =	$929.60		$1,017.7316	$1,017.73	$1,017.75	$1,017.70