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	$28.94	10.295%	$31.9194	$31.92	$31.90	$31.90
Purchase #2	$164.38	13.358%	$186.3379	$186.34	$186.35	$186.30
Purchase #3	$193.30	12.439%	$217.3446	$217.34	$217.35	$217.30
Purchase #4	$75.80	4.119%	$78.9222	$78.92	$78.90	$78.90
Purchase #5	$100.79	3.790%	$104.6099	$104.61	$104.60	$104.60
Purchase #6	$138.25	11.147%	$153.6607	$153.66	$153.65	$153.70
Purchase #7	$222.74	13.361%	$252.5003	$252.50	$252.50	$252.50
7 purchase totals =	$924.20		$1,025.2950	$1,025.29	$1,025.25	$1,025.20