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	$219.53	8.641%	$238.4996	$238.50	$238.50	$238.50
Purchase #2	$136.90	11.271%	$152.33	$152.33	$152.35	$152.30
Purchase #3	$208.69	5.168%	$219.4751	$219.48	$219.50	$219.50
Purchase #4	$37.32	12.232%	$41.885	$41.89	$41.90	$41.90
Purchase #5	$164.91	12.469%	$185.4726	$185.47	$185.45	$185.50
Purchase #6	$114.79	6.528%	$122.2835	$122.28	$122.30	$122.30
Purchase #7	$153.34	7.269%	$164.4863	$164.49	$164.50	$164.50
7 purchase totals =	$1,035.48		$1,124.4321	$1,124.44	$1,124.50	$1,124.50