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	$78.81	7.681%	$84.8634	$84.86	$84.85	$84.90
Purchase #2	$116.39	6.143%	$123.5398	$123.54	$123.55	$123.50
Purchase #3	$92.67	11.746%	$103.555	$103.56	$103.55	$103.60
Purchase #4	$112.94	10.466%	$124.7603	$124.76	$124.75	$124.80
Purchase #5	$154.71	13.700%	$175.9053	$175.91	$175.90	$175.90
Purchase #6	$24.52	7.118%	$26.2653	$26.27	$26.25	$26.30
Purchase #7	$245.90	13.264%	$278.5162	$278.52	$278.50	$278.50
7 purchase totals =	$825.94		$917.4053	$917.42	$917.35	$917.50