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	$87.78	8.410%	$95.1623	$95.16	$95.15	$95.20
Purchase #2	$216.33	12.110%	$242.5276	$242.53	$242.55	$242.50
Purchase #3	$71.62	9.560%	$78.4669	$78.47	$78.45	$78.50
Purchase #4	$211.60	10.200%	$233.1832	$233.18	$233.20	$233.20
Purchase #5	$22.84	6.708%	$24.3721	$24.37	$24.35	$24.40
Purchase #6	$144.53	8.109%	$156.2499	$156.25	$156.25	$156.20
Purchase #7	$46.81	12.239%	$52.5391	$52.54	$52.55	$52.50
7 purchase totals =	$801.51		$882.5011	$882.50	$882.50	$882.50