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	$113.90	11.523%	$127.0247	$127.02	$127.00	$127.00
Purchase #2	$106.54	4.666%	$111.5112	$111.51	$111.50	$111.50
Purchase #3	$200.76	7.785%	$216.3892	$216.39	$216.40	$216.40
Purchase #4	$218.72	5.225%	$230.1481	$230.15	$230.15	$230.10
Purchase #5	$32.69	6.798%	$34.9123	$34.91	$34.90	$34.90
Purchase #6	$54.39	5.463%	$57.3613	$57.36	$57.35	$57.40
Purchase #7	$155.67	9.486%	$170.4369	$170.44	$170.45	$170.40
7 purchase totals =	$882.67		$947.7837	$947.78	$947.75	$947.70