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	$145.73	12.805%	$164.3907	$164.39	$164.40	$164.40
Purchase #2	$54.50	8.524%	$59.1456	$59.15	$59.15	$59.10
Purchase #3	$194.64	11.580%	$217.1793	$217.18	$217.20	$217.20
Purchase #4	$61.25	7.673%	$65.9497	$65.95	$65.95	$65.90
Purchase #5	$145.96	3.130%	$150.5285	$150.53	$150.55	$150.50
Purchase #6	$103.83	9.366%	$113.5547	$113.55	$113.55	$113.60
Purchase #7	$122.49	11.694%	$136.814	$136.81	$136.80	$136.80
7 purchase totals =	$828.40		$907.5625	$907.56	$907.60	$907.50