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	$44.95	7.756%	$48.4363	$48.44	$48.45	$48.40
Purchase #2	$250.71	12.647%	$282.4173	$282.42	$282.40	$282.40
Purchase #3	$38.53	13.478%	$43.7231	$43.72	$43.70	$43.70
Purchase #4	$78.42	5.869%	$83.0225	$83.02	$83.00	$83.00
Purchase #5	$203.98	10.717%	$225.8405	$225.84	$225.85	$225.80
Purchase #6	$85.86	5.373%	$90.4733	$90.47	$90.45	$90.50
Purchase #7	$203.57	12.560%	$229.1384	$229.14	$229.15	$229.10
7 purchase totals =	$906.02		$1,003.0514	$1,003.05	$1,003.00	$1,002.90