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	$12.71	11.235%	$14.138	$14.14	$14.15	$14.10
Purchase #2	$37.26	8.589%	$40.4603	$40.46	$40.45	$40.50
Purchase #3	$55.84	11.549%	$62.289	$62.29	$62.30	$62.30
Purchase #4	$129.85	5.459%	$136.9385	$136.94	$136.95	$136.90
Purchase #5	$91.83	8.602%	$99.7292	$99.73	$99.75	$99.70
Purchase #6	$208.67	12.298%	$234.3322	$234.33	$234.35	$234.30
Purchase #7	$39.51	11.102%	$43.8964	$43.90	$43.90	$43.90
7 purchase totals =	$575.67		$631.7836	$631.79	$631.85	$631.70