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	$144.67	11.791%	$161.728	$161.73	$161.75	$161.70
Purchase #2	$96.88	13.422%	$109.8832	$109.88	$109.90	$109.90
Purchase #3	$185.84	5.624%	$196.2916	$196.29	$196.30	$196.30
Purchase #4	$50.34	11.202%	$55.9791	$55.98	$56.00	$56.00
Purchase #5	$34.34	6.319%	$36.5099	$36.51	$36.50	$36.50
Purchase #6	$149.76	3.414%	$154.8728	$154.87	$154.85	$154.90
Purchase #7	$198.88	8.490%	$215.7649	$215.76	$215.75	$215.80
7 purchase totals =	$860.71		$931.0295	$931.02	$931.05	$931.10