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	$198.50	13.596%	$225.4881	$225.49	$225.50	$225.50
Purchase #2	$199.90	7.173%	$214.2388	$214.24	$214.25	$214.20
Purchase #3	$49.81	8.758%	$54.1724	$54.17	$54.15	$54.20
Purchase #4	$169.25	12.701%	$190.7464	$190.75	$190.75	$190.70
Purchase #5	$168.53	3.119%	$173.7865	$173.79	$173.80	$173.80
Purchase #6	$98.32	10.748%	$108.8874	$108.89	$108.90	$108.90
Purchase #7	$32.69	8.691%	$35.5311	$35.53	$35.55	$35.50
7 purchase totals =	$917.00		$1,002.8507	$1,002.86	$1,002.90	$1,002.80