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	$32.88	7.481%	$35.3398	$35.34	$35.35	$35.30
Purchase #2	$246.29	10.590%	$272.3721	$272.37	$272.35	$272.40
Purchase #3	$35.41	13.674%	$40.252	$40.25	$40.25	$40.30
Purchase #4	$69.34	13.833%	$78.9318	$78.93	$78.95	$78.90
Purchase #5	$204.51	8.400%	$221.6888	$221.69	$221.70	$221.70
Purchase #6	$196.44	10.186%	$216.4494	$216.45	$216.45	$216.40
Purchase #7	$83.59	7.446%	$89.8141	$89.81	$89.80	$89.80
7 purchase totals =	$868.46		$954.8480	$954.84	$954.85	$954.80