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	$93.56	10.347%	$103.2407	$103.24	$103.25	$103.20
Purchase #2	$93.68	12.232%	$105.1389	$105.14	$105.15	$105.10
Purchase #3	$242.39	5.542%	$255.8233	$255.82	$255.80	$255.80
Purchase #4	$33.57	8.794%	$36.5221	$36.52	$36.50	$36.50
Purchase #5	$67.39	9.644%	$73.8891	$73.89	$73.90	$73.90
Purchase #6	$136.64	10.236%	$150.6265	$150.63	$150.65	$150.60
Purchase #7	$36.81	10.366%	$40.6257	$40.63	$40.65	$40.60
7 purchase totals =	$704.04		$765.8663	$765.87	$765.90	$765.70