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	$245.72	3.174%	$253.5192	$253.52	$253.50	$253.50
Purchase #2	$42.77	13.367%	$48.4871	$48.49	$48.50	$48.50
Purchase #3	$50.51	10.296%	$55.7105	$55.71	$55.70	$55.70
Purchase #4	$219.44	5.588%	$231.7023	$231.70	$231.70	$231.70
Purchase #5	$54.33	10.244%	$59.8956	$59.90	$59.90	$59.90
Purchase #6	$66.36	8.359%	$71.907	$71.91	$71.90	$71.90
Purchase #7	$14.97	10.354%	$16.52	$16.52	$16.50	$16.50
7 purchase totals =	$694.10		$737.7417	$737.75	$737.70	$737.70