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	$102.61	8.413%	$111.2426	$111.24	$111.25	$111.20
Purchase #2	$98.94	6.273%	$105.1465	$105.15	$105.15	$105.10
Purchase #3	$234.37	10.375%	$258.6859	$258.69	$258.70	$258.70
Purchase #4	$223.35	11.219%	$248.4076	$248.41	$248.40	$248.40
Purchase #5	$224.81	8.605%	$244.1549	$244.15	$244.15	$244.20
Purchase #6	$92.88	8.653%	$100.9169	$100.92	$100.90	$100.90
Purchase #7	$187.81	5.665%	$198.4494	$198.45	$198.45	$198.40
7 purchase totals =	$1,164.77		$1,267.0038	$1,267.01	$1,267.00	$1,266.90