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	$121.59	7.347%	$130.5232	$130.52	$130.50	$130.50
Purchase #2	$152.32	8.231%	$164.8575	$164.86	$164.85	$164.90
Purchase #3	$40.83	6.348%	$43.4219	$43.42	$43.40	$43.40
Purchase #4	$231.83	4.334%	$241.8775	$241.88	$241.90	$241.90
Purchase #5	$178.83	9.321%	$195.4987	$195.50	$195.50	$195.50
Purchase #6	$178.66	4.414%	$186.5461	$186.55	$186.55	$186.50
Purchase #7	$216.39	7.293%	$232.1713	$232.17	$232.15	$232.20
7 purchase totals =	$1,120.45		$1,194.8962	$1,194.90	$1,194.85	$1,194.90