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	$224.72	3.505%	$232.5964	$232.60	$232.60	$232.60
Purchase #2	$119.38	10.171%	$131.5221	$131.52	$131.50	$131.50
Purchase #3	$48.82	11.629%	$54.4973	$54.50	$54.50	$54.50
Purchase #4	$184.54	7.840%	$199.0079	$199.01	$199.00	$199.00
Purchase #5	$11.90	6.166%	$12.6338	$12.63	$12.65	$12.60
Purchase #6	$110.31	13.510%	$125.2129	$125.21	$125.20	$125.20
Purchase #7	$123.88	10.520%	$136.9122	$136.91	$136.90	$136.90
7 purchase totals =	$823.55		$892.3826	$892.38	$892.35	$892.30