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	$206.80	12.133%	$231.891	$231.89	$231.90	$231.90
Purchase #2	$39.89	8.457%	$43.2635	$43.26	$43.25	$43.30
Purchase #3	$247.64	5.314%	$260.7996	$260.80	$260.80	$260.80
Purchase #4	$130.67	11.146%	$145.2345	$145.23	$145.25	$145.20
Purchase #5	$125.78	3.729%	$130.4703	$130.47	$130.45	$130.50
Purchase #6	$112.98	3.138%	$116.5253	$116.53	$116.55	$116.50
Purchase #7	$84.31	5.795%	$89.1958	$89.20	$89.20	$89.20
7 purchase totals =	$948.07		$1,017.3800	$1,017.38	$1,017.40	$1,017.40