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	$51.76	3.138%	$53.3842	$53.38	$53.40	$53.40
Purchase #2	$77.62	6.143%	$82.3882	$82.39	$82.40	$82.40
Purchase #3	$240.51	6.176%	$255.3639	$255.36	$255.35	$255.40
Purchase #4	$221.49	8.113%	$239.4595	$239.46	$239.45	$239.50
Purchase #5	$161.99	6.655%	$172.7704	$172.77	$172.75	$172.80
Purchase #6	$65.51	9.797%	$71.928	$71.93	$71.95	$71.90
Purchase #7	$71.75	11.755%	$80.1842	$80.18	$80.20	$80.20
7 purchase totals =	$890.63		$955.4784	$955.47	$955.50	$955.60