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	$72.35	6.612%	$77.1338	$77.13	$77.15	$77.10
Purchase #2	$176.43	11.591%	$196.88	$196.88	$196.90	$196.90
Purchase #3	$139.44	11.379%	$155.3069	$155.31	$155.30	$155.30
Purchase #4	$5.32	10.656%	$5.8869	$5.89	$5.90	$5.90
Purchase #5	$152.42	11.800%	$170.4056	$170.41	$170.40	$170.40
Purchase #6	$62.25	12.165%	$69.8227	$69.82	$69.80	$69.80
Purchase #7	$119.28	5.278%	$125.5756	$125.58	$125.60	$125.60
7 purchase totals =	$727.49		$801.0115	$801.02	$801.05	$801.00