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	$204.34	9.243%	$223.2271	$223.23	$223.25	$223.20
Purchase #2	$43.50	4.480%	$45.4488	$45.45	$45.45	$45.40
Purchase #3	$223.90	7.577%	$240.8649	$240.86	$240.85	$240.90
Purchase #4	$180.96	9.723%	$198.5547	$198.55	$198.55	$198.60
Purchase #5	$108.74	12.219%	$122.0269	$122.03	$122.05	$122.00
Purchase #6	$40.28	5.454%	$42.4769	$42.48	$42.50	$42.50
Purchase #7	$151.50	13.792%	$172.3949	$172.39	$172.40	$172.40
7 purchase totals =	$953.22		$1,044.9942	$1,044.99	$1,045.05	$1,045.00