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	$209.72	6.851%	$224.0879	$224.09	$224.10	$224.10
Purchase #2	$109.67	3.816%	$113.855	$113.86	$113.85	$113.90
Purchase #3	$139.56	4.488%	$145.8235	$145.82	$145.80	$145.80
Purchase #4	$31.28	7.104%	$33.5021	$33.50	$33.50	$33.50
Purchase #5	$183.43	13.712%	$208.5819	$208.58	$208.60	$208.60
Purchase #6	$170.31	9.377%	$186.28	$186.28	$186.30	$186.30
Purchase #7	$250.31	8.843%	$272.4449	$272.44	$272.45	$272.40
7 purchase totals =	$1,094.28		$1,184.5753	$1,184.57	$1,184.60	$1,184.60