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	$124.87	9.185%	$136.3393	$136.34	$136.35	$136.30
Purchase #2	$175.76	5.451%	$185.3407	$185.34	$185.35	$185.30
Purchase #3	$232.57	11.590%	$259.5249	$259.52	$259.50	$259.50
Purchase #4	$153.42	5.503%	$161.8627	$161.86	$161.85	$161.90
Purchase #5	$135.90	12.181%	$152.454	$152.45	$152.45	$152.50
Purchase #6	$228.25	11.497%	$254.4919	$254.49	$254.50	$254.50
Purchase #7	$19.73	11.712%	$22.0408	$22.04	$22.05	$22.00
7 purchase totals =	$1,070.50		$1,172.0543	$1,172.04	$1,172.05	$1,172.00