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	$53.64	7.625%	$57.7301	$57.73	$57.75	$57.70
Purchase #2	$218.90	5.632%	$231.2284	$231.23	$231.25	$231.20
Purchase #3	$48.81	10.335%	$53.8545	$53.85	$53.85	$53.90
Purchase #4	$159.88	13.808%	$181.9562	$181.96	$181.95	$182.00
Purchase #5	$33.38	6.771%	$35.6402	$35.64	$35.65	$35.60
Purchase #6	$152.44	13.807%	$173.4874	$173.49	$173.50	$173.50
Purchase #7	$65.96	10.513%	$72.8944	$72.89	$72.90	$72.90
7 purchase totals =	$733.01		$806.7912	$806.79	$806.85	$806.80