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	$96.43	8.344%	$104.4761	$104.48	$104.50	$104.50
Purchase #2	$183.96	6.802%	$196.473	$196.47	$196.45	$196.50
Purchase #3	$236.70	13.846%	$269.4735	$269.47	$269.45	$269.50
Purchase #4	$64.60	3.459%	$66.8345	$66.83	$66.85	$66.80
Purchase #5	$6.61	3.791%	$6.8606	$6.86	$6.85	$6.90
Purchase #6	$17.94	6.697%	$19.1414	$19.14	$19.15	$19.10
Purchase #7	$216.33	12.719%	$243.845	$243.85	$243.85	$243.80
7 purchase totals =	$822.57		$907.1041	$907.10	$907.10	$907.10