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	$237.74	7.419%	$255.3779	$255.38	$255.40	$255.40
Purchase #2	$81.43	12.218%	$91.3791	$91.38	$91.40	$91.40
Purchase #3	$45.76	6.686%	$48.8195	$48.82	$48.80	$48.80
Purchase #4	$12.43	12.686%	$14.0069	$14.01	$14.00	$14.00
Purchase #5	$153.37	4.742%	$160.6428	$160.64	$160.65	$160.60
Purchase #6	$50.50	8.158%	$54.6198	$54.62	$54.60	$54.60
Purchase #7	$245.70	11.421%	$273.7614	$273.76	$273.75	$273.80
7 purchase totals =	$826.93		$898.6074	$898.61	$898.60	$898.60