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	$67.90	8.470%	$73.6511	$73.65	$73.65	$73.70
Purchase #2	$165.39	13.143%	$187.1272	$187.13	$187.15	$187.10
Purchase #3	$30.31	3.768%	$31.4521	$31.45	$31.45	$31.50
Purchase #4	$236.71	8.154%	$256.0113	$256.01	$256.00	$256.00
Purchase #5	$134.52	12.202%	$150.9341	$150.93	$150.95	$150.90
Purchase #6	$37.32	6.708%	$39.8234	$39.82	$39.80	$39.80
Purchase #7	$48.71	12.709%	$54.9006	$54.90	$54.90	$54.90
7 purchase totals =	$720.86		$793.8998	$793.89	$793.90	$793.90