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	$228.35	6.271%	$242.6698	$242.67	$242.65	$242.70
Purchase #2	$197.89	6.392%	$210.5391	$210.54	$210.55	$210.50
Purchase #3	$144.39	12.582%	$162.5571	$162.56	$162.55	$162.60
Purchase #4	$19.39	9.479%	$21.228	$21.23	$21.25	$21.20
Purchase #5	$96.36	13.726%	$109.5864	$109.59	$109.60	$109.60
Purchase #6	$250.34	8.824%	$272.43	$272.43	$272.45	$272.40
Purchase #7	$232.61	11.142%	$258.5274	$258.53	$258.55	$258.50
7 purchase totals =	$1,169.33		$1,277.5378	$1,277.55	$1,277.60	$1,277.50