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	$43.80	12.468%	$49.261	$49.26	$49.25	$49.30
Purchase #2	$95.63	13.166%	$108.2206	$108.22	$108.20	$108.20
Purchase #3	$72.48	8.315%	$78.5067	$78.51	$78.50	$78.50
Purchase #4	$248.47	13.299%	$281.514	$281.51	$281.50	$281.50
Purchase #5	$173.82	7.248%	$186.4185	$186.42	$186.40	$186.40
Purchase #6	$162.61	3.846%	$168.864	$168.86	$168.85	$168.90
Purchase #7	$88.64	7.117%	$94.9485	$94.95	$94.95	$94.90
7 purchase totals =	$885.45		$967.7333	$967.73	$967.65	$967.70