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	$152.71	8.143%	$165.1452	$165.15	$165.15	$165.10
Purchase #2	$121.31	4.675%	$126.9812	$126.98	$127.00	$127.00
Purchase #3	$92.81	7.864%	$100.1086	$100.11	$100.10	$100.10
Purchase #4	$213.67	12.426%	$240.2206	$240.22	$240.20	$240.20
Purchase #5	$188.32	9.107%	$205.4703	$205.47	$205.45	$205.50
Purchase #6	$159.94	6.260%	$169.9522	$169.95	$169.95	$170.00
Purchase #7	$224.72	10.650%	$248.6527	$248.65	$248.65	$248.70
7 purchase totals =	$1,153.48		$1,256.5308	$1,256.53	$1,256.50	$1,256.60