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	$216.81	4.330%	$226.1979	$226.20	$226.20	$226.20
Purchase #2	$235.81	11.394%	$262.6782	$262.68	$262.70	$262.70
Purchase #3	$137.56	3.568%	$142.4681	$142.47	$142.45	$142.50
Purchase #4	$71.50	4.760%	$74.9034	$74.90	$74.90	$74.90
Purchase #5	$95.86	9.710%	$105.168	$105.17	$105.15	$105.20
Purchase #6	$168.36	9.872%	$184.9805	$184.98	$185.00	$185.00
Purchase #7	$79.97	13.157%	$90.4917	$90.49	$90.50	$90.50
7 purchase totals =	$1,005.87		$1,086.8878	$1,086.89	$1,086.90	$1,087.00