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	$209.28	13.202%	$236.9091	$236.91	$236.90	$236.90
Purchase #2	$148.90	5.193%	$156.6324	$156.63	$156.65	$156.60
Purchase #3	$214.25	11.624%	$239.1544	$239.15	$239.15	$239.20
Purchase #4	$213.38	4.218%	$222.3804	$222.38	$222.40	$222.40
Purchase #5	$33.71	8.750%	$36.6596	$36.66	$36.65	$36.70
Purchase #6	$168.91	7.857%	$182.1813	$182.18	$182.20	$182.20
Purchase #7	$33.84	12.143%	$37.9492	$37.95	$37.95	$37.90
7 purchase totals =	$1,022.27		$1,111.8664	$1,111.86	$1,111.90	$1,111.90