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	$139.63	8.335%	$151.2682	$151.27	$151.25	$151.30
Purchase #2	$60.40	3.389%	$62.447	$62.45	$62.45	$62.40
Purchase #3	$89.97	3.382%	$93.0128	$93.01	$93.00	$93.00
Purchase #4	$39.34	3.604%	$40.7578	$40.76	$40.75	$40.80
Purchase #5	$7.82	9.765%	$8.5836	$8.58	$8.60	$8.60
Purchase #6	$200.25	13.746%	$227.7764	$227.78	$227.80	$227.80
Purchase #7	$35.46	6.413%	$37.734	$37.73	$37.75	$37.70
7 purchase totals =	$572.87		$621.5798	$621.58	$621.60	$621.60