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	$162.70	12.576%	$183.1612	$183.16	$183.15	$183.20
Purchase #2	$71.34	13.106%	$80.6898	$80.69	$80.70	$80.70
Purchase #3	$75.85	9.190%	$82.8206	$82.82	$82.80	$82.80
Purchase #4	$218.57	4.640%	$228.7116	$228.71	$228.70	$228.70
Purchase #5	$59.69	3.344%	$61.686	$61.69	$61.70	$61.70
Purchase #6	$130.32	9.597%	$142.8268	$142.83	$142.85	$142.80
Purchase #7	$158.34	12.637%	$178.3494	$178.35	$178.35	$178.30
7 purchase totals =	$876.81		$958.2454	$958.25	$958.25	$958.20