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	$94.49	9.400%	$103.3721	$103.37	$103.35	$103.40
Purchase #2	$203.31	13.242%	$230.2323	$230.23	$230.25	$230.20
Purchase #3	$249.53	13.526%	$283.2814	$283.28	$283.30	$283.30
Purchase #4	$133.61	4.217%	$139.2443	$139.24	$139.25	$139.20
Purchase #5	$88.46	5.689%	$93.4925	$93.49	$93.50	$93.50
Purchase #6	$39.25	10.149%	$43.2335	$43.23	$43.25	$43.20
Purchase #7	$148.35	13.348%	$168.1518	$168.15	$168.15	$168.20
7 purchase totals =	$957.00		$1,061.0079	$1,060.99	$1,061.05	$1,061.00