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	$247.98	5.290%	$261.0981	$261.10	$261.10	$261.10
Purchase #2	$106.72	4.149%	$111.1478	$111.15	$111.15	$111.10
Purchase #3	$36.38	10.558%	$40.221	$40.22	$40.20	$40.20
Purchase #4	$21.38	4.266%	$22.2921	$22.29	$22.30	$22.30
Purchase #5	$58.69	13.118%	$66.389	$66.39	$66.40	$66.40
Purchase #6	$121.49	7.495%	$130.5957	$130.60	$130.60	$130.60
Purchase #7	$31.73	7.765%	$34.1938	$34.19	$34.20	$34.20
7 purchase totals =	$624.37		$665.9375	$665.94	$665.95	$665.90