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	$186.74	13.423%	$211.8061	$211.81	$211.80	$211.80
Purchase #2	$13.34	8.488%	$14.4723	$14.47	$14.45	$14.50
Purchase #3	$214.99	13.253%	$243.4826	$243.48	$243.50	$243.50
Purchase #4	$247.79	8.526%	$268.9166	$268.92	$268.90	$268.90
Purchase #5	$213.64	6.476%	$227.4753	$227.48	$227.50	$227.50
Purchase #6	$112.28	10.401%	$123.9582	$123.96	$123.95	$124.00
Purchase #7	$120.98	5.262%	$127.346	$127.35	$127.35	$127.30
7 purchase totals =	$1,109.76		$1,217.4571	$1,217.47	$1,217.45	$1,217.50