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	$175.95	6.633%	$187.6208	$187.62	$187.60	$187.60
Purchase #2	$109.98	13.154%	$124.4468	$124.45	$124.45	$124.40
Purchase #3	$99.89	3.680%	$103.566	$103.57	$103.55	$103.60
Purchase #4	$18.81	12.457%	$21.1532	$21.15	$21.15	$21.20
Purchase #5	$214.44	3.408%	$221.7481	$221.75	$221.75	$221.70
Purchase #6	$84.27	8.768%	$91.6588	$91.66	$91.65	$91.70
Purchase #7	$233.91	8.307%	$253.3409	$253.34	$253.35	$253.30
7 purchase totals =	$937.25		$1,003.5346	$1,003.54	$1,003.50	$1,003.50