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	$40.29	12.612%	$45.3714	$45.37	$45.35	$45.40
Purchase #2	$239.43	3.535%	$247.8939	$247.89	$247.90	$247.90
Purchase #3	$60.97	10.761%	$67.531	$67.53	$67.55	$67.50
Purchase #4	$88.29	7.691%	$95.0804	$95.08	$95.10	$95.10
Purchase #5	$185.53	3.804%	$192.5876	$192.59	$192.60	$192.60
Purchase #6	$18.84	12.821%	$21.2555	$21.26	$21.25	$21.30
Purchase #7	$140.28	10.581%	$155.123	$155.12	$155.10	$155.10
7 purchase totals =	$773.63		$824.8428	$824.84	$824.85	$824.90