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	$132.29	13.317%	$149.9071	$149.91	$149.90	$149.90
Purchase #2	$194.30	8.854%	$211.5033	$211.50	$211.50	$211.50
Purchase #3	$240.33	8.314%	$260.311	$260.31	$260.30	$260.30
Purchase #4	$128.81	6.611%	$137.3256	$137.33	$137.35	$137.30
Purchase #5	$146.98	3.395%	$151.97	$151.97	$151.95	$152.00
Purchase #6	$67.61	13.263%	$76.5771	$76.58	$76.60	$76.60
Purchase #7	$89.89	12.246%	$100.8979	$100.90	$100.90	$100.90
7 purchase totals =	$1,000.21		$1,088.4920	$1,088.50	$1,088.50	$1,088.50