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	$61.50	13.625%	$69.8794	$69.88	$69.90	$69.90
Purchase #2	$162.49	9.273%	$177.5577	$177.56	$177.55	$177.60
Purchase #3	$152.69	12.651%	$172.0068	$172.01	$172.00	$172.00
Purchase #4	$250.59	5.129%	$263.4428	$263.44	$263.45	$263.40
Purchase #5	$14.54	4.151%	$15.1436	$15.14	$15.15	$15.10
Purchase #6	$218.71	13.846%	$248.9926	$248.99	$249.00	$249.00
Purchase #7	$147.39	3.443%	$152.4646	$152.46	$152.45	$152.50
7 purchase totals =	$1,007.91		$1,099.4875	$1,099.48	$1,099.50	$1,099.50