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	$130.63	13.280%	$147.9777	$147.98	$148.00	$148.00
Purchase #2	$226.68	13.680%	$257.6898	$257.69	$257.70	$257.70
Purchase #3	$108.75	13.444%	$123.3704	$123.37	$123.35	$123.40
Purchase #4	$243.82	11.127%	$270.9499	$270.95	$270.95	$270.90
Purchase #5	$55.27	7.517%	$59.4246	$59.42	$59.40	$59.40
Purchase #6	$104.94	5.338%	$110.5417	$110.54	$110.55	$110.50
Purchase #7	$58.45	7.323%	$62.7303	$62.73	$62.75	$62.70
7 purchase totals =	$928.54		$1,032.6844	$1,032.68	$1,032.70	$1,032.60