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	$232.90	6.248%	$247.4516	$247.45	$247.45	$247.50
Purchase #2	$206.67	6.391%	$219.8783	$219.88	$219.90	$219.90
Purchase #3	$13.81	12.544%	$15.5423	$15.54	$15.55	$15.50
Purchase #4	$41.60	13.238%	$47.107	$47.11	$47.10	$47.10
Purchase #5	$60.89	11.325%	$67.7858	$67.79	$67.80	$67.80
Purchase #6	$214.64	3.852%	$222.9079	$222.91	$222.90	$222.90
Purchase #7	$190.94	11.250%	$212.4208	$212.42	$212.40	$212.40
7 purchase totals =	$961.45		$1,033.0937	$1,033.10	$1,033.10	$1,033.10