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	$198.80	13.239%	$225.1191	$225.12	$225.10	$225.10
Purchase #2	$200.35	12.153%	$224.6985	$224.70	$224.70	$224.70
Purchase #3	$137.83	13.152%	$155.9574	$155.96	$155.95	$156.00
Purchase #4	$131.91	7.566%	$141.8903	$141.89	$141.90	$141.90
Purchase #5	$43.63	10.220%	$48.089	$48.09	$48.10	$48.10
Purchase #6	$231.82	5.353%	$244.2293	$244.23	$244.25	$244.20
Purchase #7	$38.48	9.446%	$42.1148	$42.11	$42.10	$42.10
7 purchase totals =	$982.82		$1,082.0984	$1,082.10	$1,082.10	$1,082.10