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	$46.45	12.404%	$52.2117	$52.21	$52.20	$52.20
Purchase #2	$86.90	4.655%	$90.9452	$90.95	$90.95	$90.90
Purchase #3	$99.45	3.747%	$103.1764	$103.18	$103.20	$103.20
Purchase #4	$143.55	11.399%	$159.9133	$159.91	$159.90	$159.90
Purchase #5	$31.87	9.648%	$34.9448	$34.94	$34.95	$34.90
Purchase #6	$96.75	3.513%	$100.1488	$100.15	$100.15	$100.10
Purchase #7	$61.37	8.140%	$66.3655	$66.37	$66.35	$66.40
7 purchase totals =	$566.34		$607.7057	$607.71	$607.70	$607.60