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	$51.78	3.226%	$53.4504	$53.45	$53.45	$53.50
Purchase #2	$213.87	12.513%	$240.6316	$240.63	$240.65	$240.60
Purchase #3	$127.97	7.430%	$137.4782	$137.48	$137.50	$137.50
Purchase #4	$159.75	13.602%	$181.4792	$181.48	$181.50	$181.50
Purchase #5	$224.97	13.672%	$255.7279	$255.73	$255.75	$255.70
Purchase #6	$118.77	6.711%	$126.7407	$126.74	$126.75	$126.70
Purchase #7	$77.94	9.561%	$85.3918	$85.39	$85.40	$85.40
7 purchase totals =	$975.05		$1,080.8998	$1,080.90	$1,081.00	$1,080.90