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	$184.32	3.372%	$190.5353	$190.54	$190.55	$190.50
Purchase #2	$109.73	8.563%	$119.1262	$119.13	$119.15	$119.10
Purchase #3	$140.31	7.278%	$150.5218	$150.52	$150.50	$150.50
Purchase #4	$215.51	9.493%	$235.9684	$235.97	$235.95	$236.00
Purchase #5	$179.77	8.558%	$195.1547	$195.15	$195.15	$195.20
Purchase #6	$216.92	12.718%	$244.5079	$244.51	$244.50	$244.50
Purchase #7	$184.50	6.504%	$196.4999	$196.50	$196.50	$196.50
7 purchase totals =	$1,231.06		$1,332.3142	$1,332.32	$1,332.30	$1,332.30