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	$229.88	7.478%	$247.0704	$247.07	$247.05	$247.10
Purchase #2	$144.87	4.710%	$151.6934	$151.69	$151.70	$151.70
Purchase #3	$138.85	8.756%	$151.0077	$151.01	$151.00	$151.00
Purchase #4	$208.84	6.723%	$222.8803	$222.88	$222.90	$222.90
Purchase #5	$114.90	11.489%	$128.1009	$128.10	$128.10	$128.10
Purchase #6	$143.47	10.144%	$158.0236	$158.02	$158.00	$158.00
Purchase #7	$57.64	7.173%	$61.7745	$61.77	$61.75	$61.80
7 purchase totals =	$1,038.45		$1,120.5508	$1,120.54	$1,120.50	$1,120.60