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	$217.33	5.577%	$229.4505	$229.45	$229.45	$229.50
Purchase #2	$87.91	8.412%	$95.305	$95.31	$95.30	$95.30
Purchase #3	$134.46	11.398%	$149.7858	$149.79	$149.80	$149.80
Purchase #4	$242.51	4.109%	$252.4747	$252.47	$252.45	$252.50
Purchase #5	$174.39	7.475%	$187.4257	$187.43	$187.45	$187.40
Purchase #6	$86.77	6.234%	$92.1792	$92.18	$92.20	$92.20
Purchase #7	$82.37	8.619%	$89.4695	$89.47	$89.45	$89.50
7 purchase totals =	$1,025.74		$1,096.0904	$1,096.10	$1,096.10	$1,096.20