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	$151.41	3.349%	$156.4807	$156.48	$156.50	$156.50
Purchase #2	$156.55	6.816%	$167.2204	$167.22	$167.20	$167.20
Purchase #3	$92.86	12.864%	$104.8055	$104.81	$104.80	$104.80
Purchase #4	$151.50	10.544%	$167.4742	$167.47	$167.45	$167.50
Purchase #5	$94.77	5.639%	$100.1141	$100.11	$100.10	$100.10
Purchase #6	$67.84	4.348%	$70.7897	$70.79	$70.80	$70.80
Purchase #7	$55.49	6.567%	$59.134	$59.13	$59.15	$59.10
7 purchase totals =	$770.42		$826.0186	$826.01	$826.00	$826.00