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	$218.53	3.315%	$225.7743	$225.77	$225.75	$225.80
Purchase #2	$56.89	4.737%	$59.5849	$59.58	$59.60	$59.60
Purchase #3	$37.50	4.139%	$39.0521	$39.05	$39.05	$39.10
Purchase #4	$184.61	11.822%	$206.4346	$206.43	$206.45	$206.40
Purchase #5	$230.57	6.511%	$245.5824	$245.58	$245.60	$245.60
Purchase #6	$43.29	11.665%	$48.3398	$48.34	$48.35	$48.30
Purchase #7	$225.45	11.843%	$252.15	$252.15	$252.15	$252.20
7 purchase totals =	$996.84		$1,076.9181	$1,076.90	$1,076.95	$1,077.00