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	$122.41	7.551%	$131.6532	$131.65	$131.65	$131.70
Purchase #2	$18.89	13.870%	$21.51	$21.51	$21.50	$21.50
Purchase #3	$44.84	4.663%	$46.9309	$46.93	$46.95	$46.90
Purchase #4	$28.45	3.533%	$29.4551	$29.46	$29.45	$29.50
Purchase #5	$10.40	4.858%	$10.9052	$10.91	$10.90	$10.90
Purchase #6	$58.65	12.221%	$65.8176	$65.82	$65.80	$65.80
Purchase #7	$239.82	8.248%	$259.6004	$259.60	$259.60	$259.60
7 purchase totals =	$523.46		$565.8724	$565.88	$565.85	$565.90