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	$48.63	10.823%	$53.8932	$53.89	$53.90	$53.90
Purchase #2	$41.53	8.602%	$45.1024	$45.10	$45.10	$45.10
Purchase #3	$85.94	4.221%	$89.5675	$89.57	$89.55	$89.60
Purchase #4	$220.98	8.382%	$239.5025	$239.50	$239.50	$239.50
Purchase #5	$48.99	10.733%	$54.2481	$54.25	$54.25	$54.20
Purchase #6	$29.79	12.118%	$33.4	$33.40	$33.40	$33.40
Purchase #7	$158.74	8.446%	$172.1472	$172.15	$172.15	$172.10
7 purchase totals =	$634.60		$687.8609	$687.86	$687.85	$687.80