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	$63.82	9.507%	$69.8874	$69.89	$69.90	$69.90
Purchase #2	$199.41	9.189%	$217.7338	$217.73	$217.75	$217.70
Purchase #3	$192.27	9.109%	$209.7839	$209.78	$209.80	$209.80
Purchase #4	$224.83	5.283%	$236.7078	$236.71	$236.70	$236.70
Purchase #5	$99.79	6.119%	$105.8962	$105.90	$105.90	$105.90
Purchase #6	$11.33	13.681%	$12.8801	$12.88	$12.90	$12.90
Purchase #7	$53.98	10.385%	$59.5858	$59.59	$59.60	$59.60
7 purchase totals =	$845.43		$912.4750	$912.48	$912.55	$912.50