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	$157.56	7.534%	$169.4306	$169.43	$169.45	$169.40
Purchase #2	$83.67	13.576%	$95.029	$95.03	$95.05	$95.00
Purchase #3	$177.71	10.705%	$196.7339	$196.73	$196.75	$196.70
Purchase #4	$234.81	13.364%	$266.19	$266.19	$266.20	$266.20
Purchase #5	$164.79	10.487%	$182.0715	$182.07	$182.05	$182.10
Purchase #6	$84.47	11.780%	$94.4206	$94.42	$94.40	$94.40
Purchase #7	$174.62	12.517%	$196.4772	$196.48	$196.50	$196.50
7 purchase totals =	$1,077.63		$1,200.3528	$1,200.35	$1,200.40	$1,200.30