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	$147.57	4.480%	$154.1811	$154.18	$154.20	$154.20
Purchase #2	$148.64	5.854%	$157.3414	$157.34	$157.35	$157.30
Purchase #3	$178.41	6.341%	$189.723	$189.72	$189.70	$189.70
Purchase #4	$145.66	3.287%	$150.4478	$150.45	$150.45	$150.40
Purchase #5	$65.65	8.517%	$71.2414	$71.24	$71.25	$71.20
Purchase #6	$126.82	11.661%	$141.6085	$141.61	$141.60	$141.60
Purchase #7	$212.40	7.297%	$227.8988	$227.90	$227.90	$227.90
7 purchase totals =	$1,025.15		$1,092.4420	$1,092.44	$1,092.45	$1,092.30