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	$50.88	7.322%	$54.6054	$54.61	$54.60	$54.60
Purchase #2	$48.60	10.621%	$53.7618	$53.76	$53.75	$53.80
Purchase #3	$138.29	10.557%	$152.8893	$152.89	$152.90	$152.90
Purchase #4	$194.91	13.266%	$220.7668	$220.77	$220.75	$220.80
Purchase #5	$41.45	9.678%	$45.4615	$45.46	$45.45	$45.50
Purchase #6	$28.67	4.319%	$29.9083	$29.91	$29.90	$29.90
Purchase #7	$134.66	12.872%	$151.9934	$151.99	$152.00	$152.00
7 purchase totals =	$637.46		$709.3865	$709.39	$709.35	$709.50