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	$65.81	8.248%	$71.238	$71.24	$71.25	$71.20
Purchase #2	$31.41	5.788%	$33.228	$33.23	$33.25	$33.20
Purchase #3	$215.70	12.527%	$242.7207	$242.72	$242.70	$242.70
Purchase #4	$73.75	10.119%	$81.2128	$81.21	$81.20	$81.20
Purchase #5	$233.93	11.741%	$261.3957	$261.40	$261.40	$261.40
Purchase #6	$104.30	6.747%	$111.3371	$111.34	$111.35	$111.30
Purchase #7	$136.97	4.527%	$143.1706	$143.17	$143.15	$143.20
7 purchase totals =	$861.87		$944.3029	$944.31	$944.30	$944.20