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	$183.25	4.386%	$191.2873	$191.29	$191.30	$191.30
Purchase #2	$102.85	5.642%	$108.6528	$108.65	$108.65	$108.70
Purchase #3	$146.79	5.836%	$155.3567	$155.36	$155.35	$155.40
Purchase #4	$237.59	10.688%	$262.9836	$262.98	$263.00	$263.00
Purchase #5	$194.77	5.834%	$206.1329	$206.13	$206.15	$206.10
Purchase #6	$53.99	10.726%	$59.781	$59.78	$59.80	$59.80
Purchase #7	$33.74	11.532%	$37.6309	$37.63	$37.65	$37.60
7 purchase totals =	$952.98		$1,021.8252	$1,021.82	$1,021.90	$1,021.90