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	$131.58	4.588%	$137.6169	$137.62	$137.60	$137.60
Purchase #2	$200.88	5.761%	$212.4527	$212.45	$212.45	$212.50
Purchase #3	$147.29	7.624%	$158.5194	$158.52	$158.50	$158.50
Purchase #4	$111.29	12.265%	$124.9397	$124.94	$124.95	$124.90
Purchase #5	$180.39	5.203%	$189.7757	$189.78	$189.80	$189.80
Purchase #6	$99.78	10.684%	$110.4405	$110.44	$110.45	$110.40
Purchase #7	$209.68	9.130%	$228.8238	$228.82	$228.80	$228.80
7 purchase totals =	$1,080.89		$1,162.5687	$1,162.57	$1,162.55	$1,162.50