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	$177.27	5.558%	$187.1227	$187.12	$187.10	$187.10
Purchase #2	$203.75	9.511%	$223.1287	$223.13	$223.15	$223.10
Purchase #3	$18.64	12.523%	$20.9743	$20.97	$20.95	$21.00
Purchase #4	$95.73	4.652%	$100.1834	$100.18	$100.20	$100.20
Purchase #5	$79.82	11.511%	$89.0081	$89.01	$89.00	$89.00
Purchase #6	$169.70	12.141%	$190.3033	$190.30	$190.30	$190.30
Purchase #7	$67.84	5.105%	$71.3032	$71.30	$71.30	$71.30
7 purchase totals =	$812.75		$882.0237	$882.01	$882.00	$882.00