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	$60.46	3.306%	$62.4588	$62.46	$62.45	$62.50
Purchase #2	$42.37	4.590%	$44.3148	$44.31	$44.30	$44.30
Purchase #3	$45.72	11.301%	$50.8868	$50.89	$50.90	$50.90
Purchase #4	$250.43	5.129%	$263.2746	$263.27	$263.25	$263.30
Purchase #5	$177.58	7.477%	$190.8577	$190.86	$190.85	$190.90
Purchase #6	$6.38	12.471%	$7.1756	$7.18	$7.20	$7.20
Purchase #7	$75.58	13.332%	$85.6563	$85.66	$85.65	$85.70
7 purchase totals =	$658.52		$704.6246	$704.63	$704.60	$704.80