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	$152.64	5.822%	$161.5267	$161.53	$161.55	$161.50
Purchase #2	$237.91	13.786%	$270.7083	$270.71	$270.70	$270.70
Purchase #3	$157.64	12.799%	$177.8163	$177.82	$177.80	$177.80
Purchase #4	$120.64	8.261%	$130.6061	$130.61	$130.60	$130.60
Purchase #5	$55.64	11.297%	$61.9257	$61.93	$61.95	$61.90
Purchase #6	$117.40	11.874%	$131.3401	$131.34	$131.35	$131.30
Purchase #7	$101.43	10.332%	$111.9097	$111.91	$111.90	$111.90
7 purchase totals =	$943.30		$1,045.8329	$1,045.85	$1,045.85	$1,045.70