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	$166.41	11.321%	$185.2493	$185.25	$185.25	$185.20
Purchase #2	$91.98	9.559%	$100.7724	$100.77	$100.75	$100.80
Purchase #3	$210.63	6.445%	$224.2051	$224.21	$224.20	$224.20
Purchase #4	$103.48	13.638%	$117.5926	$117.59	$117.60	$117.60
Purchase #5	$32.32	12.273%	$36.2866	$36.29	$36.30	$36.30
Purchase #6	$65.42	6.264%	$69.5179	$69.52	$69.50	$69.50
Purchase #7	$179.35	10.634%	$198.4221	$198.42	$198.40	$198.40
7 purchase totals =	$849.59		$932.0460	$932.05	$932.00	$932.00