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	$75.76	8.757%	$82.3943	$82.39	$82.40	$82.40
Purchase #2	$184.78	13.832%	$210.3388	$210.34	$210.35	$210.30
Purchase #3	$191.28	13.521%	$217.143	$217.14	$217.15	$217.10
Purchase #4	$14.92	10.670%	$16.512	$16.51	$16.50	$16.50
Purchase #5	$55.28	8.405%	$59.9263	$59.93	$59.95	$59.90
Purchase #6	$120.43	8.466%	$130.6256	$130.63	$130.65	$130.60
Purchase #7	$131.53	7.721%	$141.6854	$141.69	$141.70	$141.70
7 purchase totals =	$773.98		$858.6254	$858.63	$858.70	$858.50