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	$33.71	11.471%	$37.5769	$37.58	$37.60	$37.60
Purchase #2	$91.69	13.484%	$104.0535	$104.05	$104.05	$104.10
Purchase #3	$166.97	10.498%	$184.4985	$184.50	$184.50	$184.50
Purchase #4	$181.31	8.611%	$196.9226	$196.92	$196.90	$196.90
Purchase #5	$222.77	4.793%	$233.4474	$233.45	$233.45	$233.40
Purchase #6	$44.50	11.701%	$49.7069	$49.71	$49.70	$49.70
Purchase #7	$17.92	10.871%	$19.8681	$19.87	$19.85	$19.90
7 purchase totals =	$758.87		$826.0739	$826.08	$826.05	$826.10