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	$57.73	6.541%	$61.5061	$61.51	$61.50	$61.50
Purchase #2	$81.35	3.142%	$83.906	$83.91	$83.90	$83.90
Purchase #3	$62.42	4.492%	$65.2239	$65.22	$65.20	$65.20
Purchase #4	$156.25	8.579%	$169.6547	$169.65	$169.65	$169.70
Purchase #5	$11.59	7.742%	$12.4873	$12.49	$12.50	$12.50
Purchase #6	$173.38	4.330%	$180.8874	$180.89	$180.90	$180.90
Purchase #7	$90.47	8.171%	$97.8623	$97.86	$97.85	$97.90
7 purchase totals =	$633.19		$671.5277	$671.53	$671.50	$671.60