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	$55.40	7.420%	$59.5107	$59.51	$59.50	$59.50
Purchase #2	$84.45	12.538%	$95.0383	$95.04	$95.05	$95.00
Purchase #3	$167.39	11.161%	$186.0724	$186.07	$186.05	$186.10
Purchase #4	$158.52	11.705%	$177.0748	$177.07	$177.05	$177.10
Purchase #5	$32.98	13.654%	$37.4831	$37.48	$37.50	$37.50
Purchase #6	$143.80	8.767%	$156.4069	$156.41	$156.40	$156.40
Purchase #7	$245.74	3.310%	$253.874	$253.87	$253.85	$253.90
7 purchase totals =	$888.28		$965.4602	$965.45	$965.40	$965.50