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	$70.65	8.484%	$76.6439	$76.64	$76.65	$76.60
Purchase #2	$92.73	13.342%	$105.102	$105.10	$105.10	$105.10
Purchase #3	$220.47	10.599%	$243.8376	$243.84	$243.85	$243.80
Purchase #4	$91.43	4.306%	$95.367	$95.37	$95.35	$95.40
Purchase #5	$206.26	12.272%	$231.5722	$231.57	$231.55	$231.60
Purchase #6	$80.97	11.424%	$90.22	$90.22	$90.20	$90.20
Purchase #7	$152.66	5.245%	$160.667	$160.67	$160.65	$160.70
7 purchase totals =	$915.17		$1,003.4097	$1,003.41	$1,003.35	$1,003.40