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	$209.25	3.142%	$215.8246	$215.82	$215.80	$215.80
Purchase #2	$242.49	12.590%	$273.0195	$273.02	$273.00	$273.00
Purchase #3	$158.28	7.695%	$170.4596	$170.46	$170.45	$170.50
Purchase #4	$53.46	11.844%	$59.7918	$59.79	$59.80	$59.80
Purchase #5	$146.97	5.783%	$155.4693	$155.47	$155.45	$155.50
Purchase #6	$152.93	3.709%	$158.6022	$158.60	$158.60	$158.60
Purchase #7	$141.75	9.843%	$155.7025	$155.70	$155.70	$155.70
7 purchase totals =	$1,105.13		$1,188.8695	$1,188.86	$1,188.80	$1,188.90