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	$143.60	8.520%	$155.8347	$155.83	$155.85	$155.80
Purchase #2	$90.39	7.187%	$96.8863	$96.89	$96.90	$96.90
Purchase #3	$43.69	8.116%	$47.2359	$47.24	$47.25	$47.20
Purchase #4	$208.67	12.553%	$234.8643	$234.86	$234.85	$234.90
Purchase #5	$241.37	3.404%	$249.5862	$249.59	$249.60	$249.60
Purchase #6	$246.45	11.568%	$274.9593	$274.96	$274.95	$275.00
Purchase #7	$112.53	7.309%	$120.7548	$120.75	$120.75	$120.80
7 purchase totals =	$1,086.70		$1,180.1215	$1,180.12	$1,180.15	$1,180.20