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	$237.53	13.294%	$269.1072	$269.11	$269.10	$269.10
Purchase #2	$223.29	13.817%	$254.142	$254.14	$254.15	$254.10
Purchase #3	$29.44	9.726%	$32.3033	$32.30	$32.30	$32.30
Purchase #4	$100.92	11.428%	$112.4531	$112.45	$112.45	$112.50
Purchase #5	$90.80	4.570%	$94.9496	$94.95	$94.95	$94.90
Purchase #6	$171.71	8.300%	$185.9619	$185.96	$185.95	$186.00
Purchase #7	$104.72	8.358%	$113.4725	$113.47	$113.45	$113.50
7 purchase totals =	$958.41		$1,062.3896	$1,062.38	$1,062.35	$1,062.40