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	$126.55	8.375%	$137.1486	$137.15	$137.15	$137.10
Purchase #2	$216.89	4.508%	$226.6674	$226.67	$226.65	$226.70
Purchase #3	$123.65	3.618%	$128.1237	$128.12	$128.10	$128.10
Purchase #4	$236.92	7.675%	$255.1036	$255.10	$255.10	$255.10
Purchase #5	$190.26	3.137%	$196.2285	$196.23	$196.25	$196.20
Purchase #6	$169.53	5.518%	$178.8847	$178.88	$178.90	$178.90
Purchase #7	$93.74	8.584%	$101.7866	$101.79	$101.80	$101.80
7 purchase totals =	$1,157.54		$1,223.9431	$1,223.94	$1,223.95	$1,223.90