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	$67.83	9.596%	$74.339	$74.34	$74.35	$74.30
Purchase #2	$55.86	8.695%	$60.717	$60.72	$60.70	$60.70
Purchase #3	$31.72	6.717%	$33.8506	$33.85	$33.85	$33.90
Purchase #4	$199.81	13.274%	$226.3328	$226.33	$226.35	$226.30
Purchase #5	$111.77	10.165%	$123.1314	$123.13	$123.15	$123.10
Purchase #6	$226.83	10.425%	$250.477	$250.48	$250.50	$250.50
Purchase #7	$151.93	10.310%	$167.594	$167.59	$167.60	$167.60
7 purchase totals =	$845.75		$936.4418	$936.44	$936.50	$936.40