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	$106.90	4.668%	$111.8901	$111.89	$111.90	$111.90
Purchase #2	$57.35	8.403%	$62.1691	$62.17	$62.15	$62.20
Purchase #3	$164.71	10.327%	$181.7196	$181.72	$181.70	$181.70
Purchase #4	$44.70	6.147%	$47.4477	$47.45	$47.45	$47.40
Purchase #5	$140.83	4.761%	$147.5349	$147.53	$147.55	$147.50
Purchase #6	$241.57	11.728%	$269.9013	$269.90	$269.90	$269.90
Purchase #7	$201.53	3.448%	$208.4788	$208.48	$208.50	$208.50
7 purchase totals =	$957.59		$1,029.1415	$1,029.14	$1,029.15	$1,029.10