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	$61.53	3.273%	$63.5439	$63.54	$63.55	$63.50
Purchase #2	$7.29	12.174%	$8.1775	$8.18	$8.20	$8.20
Purchase #3	$111.64	13.377%	$126.5741	$126.57	$126.55	$126.60
Purchase #4	$85.95	4.741%	$90.0249	$90.02	$90.00	$90.00
Purchase #5	$108.25	3.309%	$111.832	$111.83	$111.85	$111.80
Purchase #6	$64.50	11.264%	$71.7653	$71.77	$71.75	$71.80
Purchase #7	$7.90	5.355%	$8.323	$8.32	$8.30	$8.30
7 purchase totals =	$447.06		$480.2407	$480.23	$480.20	$480.20