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	$89.38	6.215%	$94.935	$94.94	$94.95	$94.90
Purchase #2	$57.78	13.266%	$65.4451	$65.45	$65.45	$65.40
Purchase #3	$68.38	5.666%	$72.2544	$72.25	$72.25	$72.30
Purchase #4	$195.55	6.523%	$208.3057	$208.31	$208.30	$208.30
Purchase #5	$139.96	8.151%	$151.3681	$151.37	$151.35	$151.40
Purchase #6	$159.61	8.823%	$173.6924	$173.69	$173.70	$173.70
Purchase #7	$123.69	13.320%	$140.1655	$140.17	$140.15	$140.20
7 purchase totals =	$834.35		$906.1662	$906.18	$906.15	$906.20