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	$165.43	11.447%	$184.3668	$184.37	$184.35	$184.40
Purchase #2	$139.55	9.570%	$152.9049	$152.90	$152.90	$152.90
Purchase #3	$149.45	11.707%	$166.9461	$166.95	$166.95	$166.90
Purchase #4	$190.53	9.735%	$209.0781	$209.08	$209.10	$209.10
Purchase #5	$61.94	6.567%	$66.0076	$66.01	$66.00	$66.00
Purchase #6	$58.72	12.629%	$66.1357	$66.14	$66.15	$66.10
Purchase #7	$102.77	13.196%	$116.3315	$116.33	$116.35	$116.30
7 purchase totals =	$868.39		$961.7707	$961.78	$961.80	$961.70