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	$187.25	11.145%	$208.119	$208.12	$208.10	$208.10
Purchase #2	$76.42	12.442%	$85.9282	$85.93	$85.95	$85.90
Purchase #3	$172.63	5.645%	$182.375	$182.38	$182.40	$182.40
Purchase #4	$53.31	6.606%	$56.8317	$56.83	$56.85	$56.80
Purchase #5	$132.62	8.472%	$143.8556	$143.86	$143.85	$143.90
Purchase #6	$148.59	8.848%	$161.7372	$161.74	$161.75	$161.70
Purchase #7	$208.63	4.667%	$218.3668	$218.37	$218.35	$218.40
7 purchase totals =	$979.45		$1,057.2135	$1,057.23	$1,057.25	$1,057.20