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	$206.50	4.741%	$216.2902	$216.29	$216.30	$216.30
Purchase #2	$75.35	10.843%	$83.5202	$83.52	$83.50	$83.50
Purchase #3	$53.72	7.544%	$57.7726	$57.77	$57.75	$57.80
Purchase #4	$43.77	11.451%	$48.7821	$48.78	$48.80	$48.80
Purchase #5	$196.47	7.525%	$211.2544	$211.25	$211.25	$211.30
Purchase #6	$131.54	7.360%	$141.2213	$141.22	$141.20	$141.20
Purchase #7	$208.35	7.298%	$223.5554	$223.56	$223.55	$223.60
7 purchase totals =	$915.70		$982.3962	$982.39	$982.35	$982.50