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	$54.85	9.218%	$59.9061	$59.91	$59.90	$59.90
Purchase #2	$81.63	10.838%	$90.4771	$90.48	$90.50	$90.50
Purchase #3	$81.41	3.580%	$84.3245	$84.32	$84.30	$84.30
Purchase #4	$136.34	8.196%	$147.5144	$147.51	$147.50	$147.50
Purchase #5	$229.40	5.103%	$241.1063	$241.11	$241.10	$241.10
Purchase #6	$144.87	12.742%	$163.3293	$163.33	$163.35	$163.30
Purchase #7	$219.44	4.872%	$230.1311	$230.13	$230.15	$230.10
7 purchase totals =	$947.94		$1,016.7888	$1,016.79	$1,016.80	$1,016.70