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	$59.57	5.163%	$62.6456	$62.65	$62.65	$62.60
Purchase #2	$168.34	11.852%	$188.2917	$188.29	$188.30	$188.30
Purchase #3	$120.39	13.831%	$137.0411	$137.04	$137.05	$137.00
Purchase #4	$243.39	10.862%	$269.827	$269.83	$269.85	$269.80
Purchase #5	$211.70	8.820%	$230.3719	$230.37	$230.35	$230.40
Purchase #6	$55.78	7.168%	$59.7783	$59.78	$59.80	$59.80
Purchase #7	$50.66	3.341%	$52.3526	$52.35	$52.35	$52.40
7 purchase totals =	$909.83		$1,000.3082	$1,000.31	$1,000.35	$1,000.30