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	$112.33	7.242%	$120.4649	$120.46	$120.45	$120.50
Purchase #2	$250.54	5.832%	$265.1515	$265.15	$265.15	$265.20
Purchase #3	$80.62	10.786%	$89.3157	$89.32	$89.30	$89.30
Purchase #4	$145.31	7.142%	$155.688	$155.69	$155.70	$155.70
Purchase #5	$225.44	12.735%	$254.1498	$254.15	$254.15	$254.10
Purchase #6	$51.62	7.754%	$55.6226	$55.62	$55.60	$55.60
Purchase #7	$137.29	12.439%	$154.3675	$154.37	$154.35	$154.40
7 purchase totals =	$1,003.15		$1,094.7600	$1,094.76	$1,094.70	$1,094.80