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	$91.29	12.460%	$102.6647	$102.66	$102.65	$102.70
Purchase #2	$180.76	8.546%	$196.2077	$196.21	$196.20	$196.20
Purchase #3	$165.31	5.461%	$174.3376	$174.34	$174.35	$174.30
Purchase #4	$37.46	11.524%	$41.7769	$41.78	$41.80	$41.80
Purchase #5	$99.92	4.475%	$104.3914	$104.39	$104.40	$104.40
Purchase #6	$56.58	10.415%	$62.4728	$62.47	$62.45	$62.50
Purchase #7	$202.70	3.491%	$209.7763	$209.78	$209.80	$209.80
7 purchase totals =	$834.02		$891.6274	$891.63	$891.65	$891.70