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	$185.55	8.118%	$200.6129	$200.61	$200.60	$200.60
Purchase #2	$49.69	11.714%	$55.5107	$55.51	$55.50	$55.50
Purchase #3	$225.53	12.829%	$254.4632	$254.46	$254.45	$254.50
Purchase #4	$199.40	5.270%	$209.9084	$209.91	$209.90	$209.90
Purchase #5	$179.47	4.662%	$187.8369	$187.84	$187.85	$187.80
Purchase #6	$5.85	4.747%	$6.1277	$6.13	$6.15	$6.10
Purchase #7	$46.59	8.130%	$50.3778	$50.38	$50.40	$50.40
7 purchase totals =	$892.08		$964.8376	$964.84	$964.85	$964.80