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	$85.57	4.235%	$89.1939	$89.19	$89.20	$89.20
Purchase #2	$6.70	12.253%	$7.521	$7.52	$7.50	$7.50
Purchase #3	$192.66	8.261%	$208.5756	$208.58	$208.60	$208.60
Purchase #4	$245.80	10.862%	$272.4988	$272.50	$272.50	$272.50
Purchase #5	$217.90	12.812%	$245.8173	$245.82	$245.80	$245.80
Purchase #6	$39.58	3.316%	$40.8925	$40.89	$40.90	$40.90
Purchase #7	$85.50	4.238%	$89.1235	$89.12	$89.10	$89.10
7 purchase totals =	$873.71		$953.6226	$953.62	$953.60	$953.60