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	$160.64	6.718%	$171.4318	$171.43	$171.45	$171.40
Purchase #2	$42.75	13.189%	$48.3883	$48.39	$48.40	$48.40
Purchase #3	$53.63	10.870%	$59.4596	$59.46	$59.45	$59.50
Purchase #4	$192.37	8.515%	$208.7503	$208.75	$208.75	$208.80
Purchase #5	$134.43	8.153%	$145.3901	$145.39	$145.40	$145.40
Purchase #6	$235.74	8.468%	$255.7025	$255.70	$255.70	$255.70
Purchase #7	$247.96	9.184%	$270.7326	$270.73	$270.75	$270.70
7 purchase totals =	$1,067.52		$1,159.8552	$1,159.85	$1,159.90	$1,159.90