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	$192.85	13.208%	$218.3216	$218.32	$218.30	$218.30
Purchase #2	$148.93	7.631%	$160.2948	$160.29	$160.30	$160.30
Purchase #3	$200.75	8.731%	$218.2775	$218.28	$218.30	$218.30
Purchase #4	$36.83	11.164%	$40.9417	$40.94	$40.95	$40.90
Purchase #5	$117.78	5.782%	$124.59	$124.59	$124.60	$124.60
Purchase #6	$208.51	3.776%	$216.3833	$216.38	$216.40	$216.40
Purchase #7	$189.39	12.312%	$212.7077	$212.71	$212.70	$212.70
7 purchase totals =	$1,095.04		$1,191.5166	$1,191.51	$1,191.55	$1,191.50