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	$199.78	8.535%	$216.8312	$216.83	$216.85	$216.80
Purchase #2	$248.75	9.201%	$271.6375	$271.64	$271.65	$271.60
Purchase #3	$32.78	13.794%	$37.3017	$37.30	$37.30	$37.30
Purchase #4	$115.59	12.822%	$130.4109	$130.41	$130.40	$130.40
Purchase #5	$66.46	10.105%	$73.1758	$73.18	$73.20	$73.20
Purchase #6	$164.28	4.297%	$171.3391	$171.34	$171.35	$171.30
Purchase #7	$237.38	11.545%	$264.7855	$264.79	$264.80	$264.80
7 purchase totals =	$1,065.02		$1,165.4817	$1,165.49	$1,165.55	$1,165.40