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	$231.96	9.708%	$254.4787	$254.48	$254.50	$254.50
Purchase #2	$111.48	4.532%	$116.5323	$116.53	$116.55	$116.50
Purchase #3	$229.28	7.540%	$246.5677	$246.57	$246.55	$246.60
Purchase #4	$204.47	12.731%	$230.5011	$230.50	$230.50	$230.50
Purchase #5	$103.30	8.143%	$111.7117	$111.71	$111.70	$111.70
Purchase #6	$195.49	8.165%	$211.4518	$211.45	$211.45	$211.50
Purchase #7	$119.48	7.799%	$128.7982	$128.80	$128.80	$128.80
7 purchase totals =	$1,195.46		$1,300.0415	$1,300.04	$1,300.05	$1,300.10