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	$33.96	10.675%	$37.5852	$37.59	$37.60	$37.60
Purchase #2	$41.27	3.794%	$42.8358	$42.84	$42.85	$42.80
Purchase #3	$92.99	4.323%	$97.01	$97.01	$97.00	$97.00
Purchase #4	$122.96	6.233%	$130.6241	$130.62	$130.60	$130.60
Purchase #5	$203.66	4.508%	$212.841	$212.84	$212.85	$212.80
Purchase #6	$139.34	8.501%	$151.1853	$151.19	$151.20	$151.20
Purchase #7	$25.54	13.336%	$28.946	$28.95	$28.95	$28.90
7 purchase totals =	$659.72		$701.0274	$701.04	$701.05	$700.90