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	$214.41	3.610%	$222.1502	$222.15	$222.15	$222.20
Purchase #2	$150.97	13.392%	$171.1879	$171.19	$171.20	$171.20
Purchase #3	$152.29	10.624%	$168.4693	$168.47	$168.45	$168.50
Purchase #4	$115.62	10.332%	$127.5659	$127.57	$127.55	$127.60
Purchase #5	$44.43	4.413%	$46.3907	$46.39	$46.40	$46.40
Purchase #6	$140.65	10.785%	$155.8191	$155.82	$155.80	$155.80
Purchase #7	$40.64	9.164%	$44.3642	$44.36	$44.35	$44.40
7 purchase totals =	$859.01		$935.9473	$935.95	$935.90	$936.10