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	$208.56	11.165%	$231.8457	$231.85	$231.85	$231.80
Purchase #2	$38.94	6.428%	$41.4431	$41.44	$41.45	$41.40
Purchase #3	$74.45	12.335%	$83.6334	$83.63	$83.65	$83.60
Purchase #4	$83.97	12.847%	$94.7576	$94.76	$94.75	$94.80
Purchase #5	$13.30	3.628%	$13.7825	$13.78	$13.80	$13.80
Purchase #6	$18.64	4.779%	$19.5308	$19.53	$19.55	$19.50
Purchase #7	$174.60	12.530%	$196.4774	$196.48	$196.50	$196.50
7 purchase totals =	$612.46		$681.4705	$681.47	$681.55	$681.40