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	$199.60	13.181%	$225.9093	$225.91	$225.90	$225.90
Purchase #2	$68.61	7.253%	$73.5863	$73.59	$73.60	$73.60
Purchase #3	$248.50	13.291%	$281.5281	$281.53	$281.55	$281.50
Purchase #4	$13.38	13.378%	$15.17	$15.17	$15.15	$15.20
Purchase #5	$189.53	12.354%	$212.9445	$212.94	$212.95	$212.90
Purchase #6	$112.85	3.789%	$117.1259	$117.13	$117.15	$117.10
Purchase #7	$210.75	6.449%	$224.3413	$224.34	$224.35	$224.30
7 purchase totals =	$1,043.22		$1,150.6054	$1,150.61	$1,150.65	$1,150.50