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	$222.41	7.280%	$238.6014	$238.60	$238.60	$238.60
Purchase #2	$187.61	10.105%	$206.568	$206.57	$206.55	$206.60
Purchase #3	$36.64	8.120%	$39.6152	$39.62	$39.60	$39.60
Purchase #4	$218.72	11.370%	$243.5885	$243.59	$243.60	$243.60
Purchase #5	$196.55	3.344%	$203.1226	$203.12	$203.10	$203.10
Purchase #6	$13.98	7.374%	$15.0109	$15.01	$15.00	$15.00
Purchase #7	$67.58	5.141%	$71.0543	$71.05	$71.05	$71.10
7 purchase totals =	$943.49		$1,017.5609	$1,017.56	$1,017.50	$1,017.60