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	$119.95	5.166%	$126.1466	$126.15	$126.15	$126.10
Purchase #2	$95.26	12.230%	$106.9103	$106.91	$106.90	$106.90
Purchase #3	$221.94	10.631%	$245.5344	$245.53	$245.55	$245.50
Purchase #4	$158.71	12.526%	$178.59	$178.59	$178.60	$178.60
Purchase #5	$67.35	7.508%	$72.4066	$72.41	$72.40	$72.40
Purchase #6	$27.82	13.421%	$31.5537	$31.55	$31.55	$31.60
Purchase #7	$133.61	5.582%	$141.0681	$141.07	$141.05	$141.10
7 purchase totals =	$824.64		$902.2097	$902.21	$902.20	$902.20