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	$157.45	3.300%	$162.6459	$162.65	$162.65	$162.60
Purchase #2	$231.25	4.717%	$242.1581	$242.16	$242.15	$242.20
Purchase #3	$59.63	9.225%	$65.1309	$65.13	$65.15	$65.10
Purchase #4	$78.80	8.553%	$85.5398	$85.54	$85.55	$85.50
Purchase #5	$200.96	13.401%	$227.8906	$227.89	$227.90	$227.90
Purchase #6	$11.74	7.589%	$12.6309	$12.63	$12.65	$12.60
Purchase #7	$102.95	6.393%	$109.5316	$109.53	$109.55	$109.50
7 purchase totals =	$842.78		$905.5278	$905.53	$905.60	$905.40