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	$196.45	5.235%	$206.7342	$206.73	$206.75	$206.70
Purchase #2	$54.42	13.378%	$61.7003	$61.70	$61.70	$61.70
Purchase #3	$203.64	3.874%	$211.529	$211.53	$211.55	$211.50
Purchase #4	$31.77	6.621%	$33.8735	$33.87	$33.85	$33.90
Purchase #5	$37.92	12.207%	$42.5489	$42.55	$42.55	$42.50
Purchase #6	$111.93	11.568%	$124.8781	$124.88	$124.90	$124.90
Purchase #7	$139.45	10.600%	$154.2317	$154.23	$154.25	$154.20
7 purchase totals =	$775.58		$835.4957	$835.49	$835.55	$835.40