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	$137.82	7.313%	$147.8988	$147.90	$147.90	$147.90
Purchase #2	$40.65	7.118%	$43.5435	$43.54	$43.55	$43.50
Purchase #3	$56.52	6.589%	$60.2441	$60.24	$60.25	$60.20
Purchase #4	$137.53	7.200%	$147.4322	$147.43	$147.45	$147.40
Purchase #5	$137.66	6.280%	$146.305	$146.31	$146.30	$146.30
Purchase #6	$90.99	9.378%	$99.523	$99.52	$99.50	$99.50
Purchase #7	$21.76	3.800%	$22.5869	$22.59	$22.60	$22.60
7 purchase totals =	$622.93		$667.5335	$667.53	$667.55	$667.40