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	$94.61	9.327%	$103.4343	$103.43	$103.45	$103.40
Purchase #2	$100.81	5.777%	$106.6338	$106.63	$106.65	$106.60
Purchase #3	$71.27	11.666%	$79.5844	$79.58	$79.60	$79.60
Purchase #4	$198.61	12.132%	$222.7054	$222.71	$222.70	$222.70
Purchase #5	$157.81	11.490%	$175.9424	$175.94	$175.95	$175.90
Purchase #6	$192.57	12.448%	$216.5411	$216.54	$216.55	$216.50
Purchase #7	$43.94	3.142%	$45.3206	$45.32	$45.30	$45.30
7 purchase totals =	$859.62		$950.1620	$950.15	$950.20	$950.00