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	$56.60	10.571%	$62.5832	$62.58	$62.60	$62.60
Purchase #2	$101.33	8.406%	$109.8478	$109.85	$109.85	$109.80
Purchase #3	$49.79	13.367%	$56.4454	$56.45	$56.45	$56.40
Purchase #4	$243.25	12.688%	$274.1136	$274.11	$274.10	$274.10
Purchase #5	$135.46	13.635%	$153.93	$153.93	$153.95	$153.90
Purchase #6	$236.72	11.573%	$264.1156	$264.12	$264.10	$264.10
Purchase #7	$230.52	13.554%	$261.7647	$261.76	$261.75	$261.80
7 purchase totals =	$1,053.67		$1,182.8003	$1,182.80	$1,182.80	$1,182.70