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	$63.35	12.683%	$71.3847	$71.38	$71.40	$71.40
Purchase #2	$248.34	3.677%	$257.4715	$257.47	$257.45	$257.50
Purchase #3	$39.57	6.311%	$42.0673	$42.07	$42.05	$42.10
Purchase #4	$229.58	6.312%	$244.0711	$244.07	$244.05	$244.10
Purchase #5	$159.50	8.142%	$172.4865	$172.49	$172.50	$172.50
Purchase #6	$204.64	10.687%	$226.5099	$226.51	$226.50	$226.50
Purchase #7	$58.32	5.516%	$61.5369	$61.54	$61.55	$61.50
7 purchase totals =	$1,003.30		$1,075.5279	$1,075.53	$1,075.50	$1,075.60