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	$148.61	3.778%	$154.2245	$154.22	$154.20	$154.20
Purchase #2	$104.36	6.386%	$111.0244	$111.02	$111.00	$111.00
Purchase #3	$63.76	12.369%	$71.6465	$71.65	$71.65	$71.60
Purchase #4	$89.51	11.853%	$100.1196	$100.12	$100.10	$100.10
Purchase #5	$50.45	4.464%	$52.7021	$52.70	$52.70	$52.70
Purchase #6	$232.88	12.466%	$261.9108	$261.91	$261.90	$261.90
Purchase #7	$139.25	3.221%	$143.7352	$143.74	$143.75	$143.70
7 purchase totals =	$828.82		$895.3631	$895.36	$895.30	$895.20