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	$38.36	11.791%	$42.883	$42.88	$42.90	$42.90
Purchase #2	$220.92	13.179%	$250.035	$250.04	$250.05	$250.00
Purchase #3	$27.72	6.738%	$29.5878	$29.59	$29.60	$29.60
Purchase #4	$212.97	8.473%	$231.0149	$231.01	$231.00	$231.00
Purchase #5	$214.77	6.378%	$228.468	$228.47	$228.45	$228.50
Purchase #6	$179.61	11.615%	$200.4717	$200.47	$200.45	$200.50
Purchase #7	$248.25	6.145%	$263.505	$263.51	$263.50	$263.50
7 purchase totals =	$1,142.60		$1,245.9654	$1,245.97	$1,245.95	$1,246.00