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	$243.57	5.576%	$257.1515	$257.15	$257.15	$257.20
Purchase #2	$40.84	4.282%	$42.5888	$42.59	$42.60	$42.60
Purchase #3	$59.59	4.373%	$62.1959	$62.20	$62.20	$62.20
Purchase #4	$53.71	4.118%	$55.9218	$55.92	$55.90	$55.90
Purchase #5	$125.41	9.592%	$137.4393	$137.44	$137.45	$137.40
Purchase #6	$120.71	9.742%	$132.4696	$132.47	$132.45	$132.50
Purchase #7	$11.30	9.561%	$12.3804	$12.38	$12.40	$12.40
7 purchase totals =	$655.13		$700.1473	$700.15	$700.15	$700.20