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	$95.92	6.473%	$102.1289	$102.13	$102.15	$102.10
Purchase #2	$236.57	8.458%	$256.5791	$256.58	$256.60	$256.60
Purchase #3	$65.81	8.454%	$71.3736	$71.37	$71.35	$71.40
Purchase #4	$242.80	10.750%	$268.901	$268.90	$268.90	$268.90
Purchase #5	$228.34	6.318%	$242.7665	$242.77	$242.75	$242.80
Purchase #6	$69.51	11.766%	$77.6885	$77.69	$77.70	$77.70
Purchase #7	$95.36	8.630%	$103.5896	$103.59	$103.60	$103.60
7 purchase totals =	$1,034.31		$1,123.0272	$1,123.03	$1,123.05	$1,123.10