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	$157.45	5.120%	$165.5114	$165.51	$165.50	$165.50
Purchase #2	$65.71	11.483%	$73.2555	$73.26	$73.25	$73.30
Purchase #3	$151.25	9.289%	$165.2996	$165.30	$165.30	$165.30
Purchase #4	$20.25	11.232%	$22.5245	$22.52	$22.50	$22.50
Purchase #5	$92.32	10.337%	$101.8631	$101.86	$101.85	$101.90
Purchase #6	$147.58	3.303%	$152.4546	$152.45	$152.45	$152.50
Purchase #7	$184.31	3.872%	$191.4465	$191.45	$191.45	$191.40
7 purchase totals =	$818.87		$872.3552	$872.35	$872.30	$872.40