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	$112.38	8.271%	$121.6749	$121.67	$121.65	$121.70
Purchase #2	$113.85	4.116%	$118.5361	$118.54	$118.55	$118.50
Purchase #3	$144.38	9.841%	$158.5884	$158.59	$158.60	$158.60
Purchase #4	$235.58	11.801%	$263.3808	$263.38	$263.40	$263.40
Purchase #5	$43.46	3.408%	$44.9411	$44.94	$44.95	$44.90
Purchase #6	$212.82	3.712%	$220.7199	$220.72	$220.70	$220.70
Purchase #7	$76.59	8.212%	$82.8796	$82.88	$82.90	$82.90
7 purchase totals =	$939.06		$1,010.7208	$1,010.72	$1,010.75	$1,010.70