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	$195.76	7.328%	$210.1053	$210.11	$210.10	$210.10
Purchase #2	$120.94	13.664%	$137.4652	$137.47	$137.45	$137.50
Purchase #3	$38.91	4.368%	$40.6096	$40.61	$40.60	$40.60
Purchase #4	$154.81	8.665%	$168.2243	$168.22	$168.20	$168.20
Purchase #5	$225.58	13.836%	$256.7912	$256.79	$256.80	$256.80
Purchase #6	$49.34	5.662%	$52.1336	$52.13	$52.15	$52.10
Purchase #7	$199.63	12.738%	$225.0589	$225.06	$225.05	$225.10
7 purchase totals =	$984.97		$1,090.3881	$1,090.39	$1,090.35	$1,090.40