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	$125.51	11.385%	$139.7993	$139.80	$139.80	$139.80
Purchase #2	$15.39	11.385%	$17.1422	$17.14	$17.15	$17.10
Purchase #3	$11.64	13.137%	$13.1691	$13.17	$13.15	$13.20
Purchase #4	$117.27	12.180%	$131.5535	$131.55	$131.55	$131.60
Purchase #5	$16.76	10.796%	$18.5694	$18.57	$18.55	$18.60
Purchase #6	$59.86	4.872%	$62.7764	$62.78	$62.80	$62.80
Purchase #7	$57.98	11.702%	$64.7648	$64.76	$64.75	$64.80
7 purchase totals =	$404.41		$447.7747	$447.77	$447.75	$447.90