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	$224.92	11.821%	$251.5078	$251.51	$251.50	$251.50
Purchase #2	$109.68	3.364%	$113.3696	$113.37	$113.35	$113.40
Purchase #3	$38.77	9.592%	$42.4888	$42.49	$42.50	$42.50
Purchase #4	$172.90	12.476%	$194.471	$194.47	$194.45	$194.50
Purchase #5	$38.26	6.165%	$40.6187	$40.62	$40.60	$40.60
Purchase #6	$196.78	6.138%	$208.8584	$208.86	$208.85	$208.90
Purchase #7	$182.58	10.147%	$201.1064	$201.11	$201.10	$201.10
7 purchase totals =	$963.89		$1,052.4207	$1,052.43	$1,052.35	$1,052.50