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	$38.53	4.181%	$40.1409	$40.14	$40.15	$40.10
Purchase #2	$55.47	8.129%	$59.9792	$59.98	$60.00	$60.00
Purchase #3	$119.56	9.703%	$131.1609	$131.16	$131.15	$131.20
Purchase #4	$57.46	11.615%	$64.134	$64.13	$64.15	$64.10
Purchase #5	$136.75	6.108%	$145.1027	$145.10	$145.10	$145.10
Purchase #6	$240.56	7.466%	$258.5202	$258.52	$258.50	$258.50
Purchase #7	$233.76	4.590%	$244.4896	$244.49	$244.50	$244.50
7 purchase totals =	$882.09		$943.5275	$943.52	$943.55	$943.50