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	$73.53	7.195%	$78.8205	$78.82	$78.80	$78.80
Purchase #2	$155.95	3.866%	$161.979	$161.98	$162.00	$162.00
Purchase #3	$187.41	9.334%	$204.9028	$204.90	$204.90	$204.90
Purchase #4	$217.27	12.808%	$245.0979	$245.10	$245.10	$245.10
Purchase #5	$40.74	12.738%	$45.9295	$45.93	$45.95	$45.90
Purchase #6	$152.52	13.145%	$172.5688	$172.57	$172.55	$172.60
Purchase #7	$142.94	5.111%	$150.2457	$150.25	$150.25	$150.20
7 purchase totals =	$970.36		$1,059.5442	$1,059.55	$1,059.55	$1,059.50