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	$125.70	11.558%	$140.2284	$140.23	$140.25	$140.20
Purchase #2	$135.50	12.440%	$152.3562	$152.36	$152.35	$152.40
Purchase #3	$69.92	3.690%	$72.5	$72.50	$72.50	$72.50
Purchase #4	$145.33	11.145%	$161.527	$161.53	$161.55	$161.50
Purchase #5	$6.66	11.547%	$7.429	$7.43	$7.45	$7.40
Purchase #6	$205.79	13.662%	$233.905	$233.91	$233.90	$233.90
Purchase #7	$30.31	9.421%	$33.1655	$33.17	$33.15	$33.20
7 purchase totals =	$719.21		$801.1111	$801.13	$801.15	$801.10