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	$126.86	9.644%	$139.0944	$139.09	$139.10	$139.10
Purchase #2	$31.61	6.384%	$33.628	$33.63	$33.65	$33.60
Purchase #3	$230.86	10.515%	$255.1349	$255.13	$255.15	$255.10
Purchase #4	$7.65	12.384%	$8.5974	$8.60	$8.60	$8.60
Purchase #5	$85.90	3.694%	$89.0731	$89.07	$89.05	$89.10
Purchase #6	$136.86	12.832%	$154.4219	$154.42	$154.40	$154.40
Purchase #7	$209.91	11.677%	$234.4212	$234.42	$234.40	$234.40
7 purchase totals =	$829.65		$914.3709	$914.36	$914.35	$914.30