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	$155.48	11.158%	$172.8285	$172.83	$172.85	$172.80
Purchase #2	$131.59	12.770%	$148.394	$148.39	$148.40	$148.40
Purchase #3	$221.67	3.615%	$229.6834	$229.68	$229.70	$229.70
Purchase #4	$30.53	6.309%	$32.4561	$32.46	$32.45	$32.50
Purchase #5	$194.41	9.835%	$213.5302	$213.53	$213.55	$213.50
Purchase #6	$75.71	12.244%	$84.9799	$84.98	$85.00	$85.00
Purchase #7	$50.67	11.527%	$56.5107	$56.51	$56.50	$56.50
7 purchase totals =	$860.06		$938.3828	$938.38	$938.45	$938.40