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	$86.84	4.528%	$90.7721	$90.77	$90.75	$90.80
Purchase #2	$83.66	12.338%	$93.982	$93.98	$94.00	$94.00
Purchase #3	$77.38	4.764%	$81.0664	$81.07	$81.05	$81.10
Purchase #4	$14.97	3.103%	$15.4345	$15.43	$15.45	$15.40
Purchase #5	$34.50	12.208%	$38.7118	$38.71	$38.70	$38.70
Purchase #6	$37.61	10.506%	$41.5613	$41.56	$41.55	$41.60
Purchase #7	$169.91	9.143%	$185.4449	$185.44	$185.45	$185.40
7 purchase totals =	$504.87		$546.9730	$546.96	$546.95	$547.00