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	$90.92	3.433%	$94.0413	$94.04	$94.05	$94.00
Purchase #2	$83.33	8.555%	$90.4589	$90.46	$90.45	$90.50
Purchase #3	$80.57	10.795%	$89.2675	$89.27	$89.25	$89.30
Purchase #4	$169.79	10.464%	$187.5568	$187.56	$187.55	$187.60
Purchase #5	$29.99	7.407%	$32.2114	$32.21	$32.20	$32.20
Purchase #6	$23.77	12.766%	$26.8045	$26.80	$26.80	$26.80
Purchase #7	$80.51	12.229%	$90.3556	$90.36	$90.35	$90.40
7 purchase totals =	$558.88		$610.6960	$610.70	$610.65	$610.80