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	$237.28	7.837%	$255.8756	$255.88	$255.90	$255.90
Purchase #2	$165.71	12.406%	$186.268	$186.27	$186.25	$186.30
Purchase #3	$60.79	12.847%	$68.5997	$68.60	$68.60	$68.60
Purchase #4	$69.54	3.748%	$72.1464	$72.15	$72.15	$72.10
Purchase #5	$39.63	9.783%	$43.507	$43.51	$43.50	$43.50
Purchase #6	$91.46	9.532%	$100.178	$100.18	$100.20	$100.20
Purchase #7	$210.73	13.820%	$239.8529	$239.85	$239.85	$239.90
7 purchase totals =	$875.14		$966.4276	$966.44	$966.45	$966.50