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	$112.83	8.562%	$122.4905	$122.49	$122.50	$122.50
Purchase #2	$135.93	4.763%	$142.4043	$142.40	$142.40	$142.40
Purchase #3	$179.77	10.313%	$198.3097	$198.31	$198.30	$198.30
Purchase #4	$61.83	9.755%	$67.8615	$67.86	$67.85	$67.90
Purchase #5	$163.98	5.186%	$172.484	$172.48	$172.50	$172.50
Purchase #6	$54.93	4.870%	$57.6051	$57.61	$57.60	$57.60
Purchase #7	$233.79	7.310%	$250.88	$250.88	$250.90	$250.90
7 purchase totals =	$943.06		$1,012.0351	$1,012.03	$1,012.05	$1,012.10