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	$173.76	9.325%	$189.9631	$189.96	$189.95	$190.00
Purchase #2	$119.76	4.313%	$124.9252	$124.93	$124.95	$124.90
Purchase #3	$171.59	11.200%	$190.8081	$190.81	$190.80	$190.80
Purchase #4	$27.25	6.507%	$29.0232	$29.02	$29.00	$29.00
Purchase #5	$73.54	3.174%	$75.8742	$75.87	$75.85	$75.90
Purchase #6	$179.61	9.456%	$196.5939	$196.59	$196.60	$196.60
Purchase #7	$86.35	4.634%	$90.3515	$90.35	$90.35	$90.40
7 purchase totals =	$831.86		$897.5392	$897.53	$897.50	$897.60