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	$132.58	12.177%	$148.7243	$148.72	$148.70	$148.70
Purchase #2	$82.28	12.557%	$92.6119	$92.61	$92.60	$92.60
Purchase #3	$32.30	11.681%	$36.073	$36.07	$36.05	$36.10
Purchase #4	$69.97	3.285%	$72.2685	$72.27	$72.25	$72.30
Purchase #5	$17.31	13.289%	$19.6103	$19.61	$19.60	$19.60
Purchase #6	$98.42	11.738%	$109.9725	$109.97	$109.95	$110.00
Purchase #7	$132.35	12.143%	$148.4213	$148.42	$148.40	$148.40
7 purchase totals =	$565.21		$627.6818	$627.67	$627.55	$627.70