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	$131.33	7.140%	$140.707	$140.71	$140.70	$140.70
Purchase #2	$213.62	9.143%	$233.1513	$233.15	$233.15	$233.20
Purchase #3	$186.79	12.167%	$209.5167	$209.52	$209.50	$209.50
Purchase #4	$155.64	6.327%	$165.4873	$165.49	$165.50	$165.50
Purchase #5	$177.62	7.873%	$191.604	$191.60	$191.60	$191.60
Purchase #6	$65.63	9.352%	$71.7677	$71.77	$71.75	$71.80
Purchase #7	$213.39	4.269%	$222.4996	$222.50	$222.50	$222.50
7 purchase totals =	$1,144.02		$1,234.7336	$1,234.74	$1,234.70	$1,234.80