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	$190.46	9.795%	$209.1156	$209.12	$209.10	$209.10
Purchase #2	$59.79	3.465%	$61.8617	$61.86	$61.85	$61.90
Purchase #3	$22.47	13.730%	$25.5551	$25.56	$25.55	$25.60
Purchase #4	$223.60	13.726%	$254.2913	$254.29	$254.30	$254.30
Purchase #5	$222.55	8.673%	$241.8518	$241.85	$241.85	$241.90
Purchase #6	$71.55	4.632%	$74.8642	$74.86	$74.85	$74.90
Purchase #7	$194.46	12.240%	$218.2619	$218.26	$218.25	$218.30
7 purchase totals =	$984.88		$1,085.8016	$1,085.80	$1,085.75	$1,086.00