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	$147.82	7.449%	$158.8311	$158.83	$158.85	$158.80
Purchase #2	$196.27	13.645%	$223.051	$223.05	$223.05	$223.10
Purchase #3	$125.41	13.776%	$142.6865	$142.69	$142.70	$142.70
Purchase #4	$37.55	12.791%	$42.353	$42.35	$42.35	$42.40
Purchase #5	$64.65	5.484%	$68.1954	$68.20	$68.20	$68.20
Purchase #6	$189.64	9.743%	$208.1166	$208.12	$208.10	$208.10
Purchase #7	$21.64	13.570%	$24.5765	$24.58	$24.60	$24.60
7 purchase totals =	$782.98		$867.8101	$867.82	$867.85	$867.90