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	$94.55	6.272%	$100.4802	$100.48	$100.50	$100.50
Purchase #2	$229.50	13.339%	$260.113	$260.11	$260.10	$260.10
Purchase #3	$63.46	6.547%	$67.6147	$67.61	$67.60	$67.60
Purchase #4	$213.98	5.144%	$224.9871	$224.99	$225.00	$225.00
Purchase #5	$114.53	5.508%	$120.8383	$120.84	$120.85	$120.80
Purchase #6	$6.57	10.789%	$7.2788	$7.28	$7.30	$7.30
Purchase #7	$229.47	10.509%	$253.585	$253.59	$253.60	$253.60
7 purchase totals =	$952.06		$1,034.8971	$1,034.90	$1,034.95	$1,034.90