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	$128.80	13.629%	$146.3542	$146.35	$146.35	$146.40
Purchase #2	$109.89	10.229%	$121.1306	$121.13	$121.15	$121.10
Purchase #3	$84.56	9.581%	$92.6617	$92.66	$92.65	$92.70
Purchase #4	$38.59	13.769%	$43.9035	$43.90	$43.90	$43.90
Purchase #5	$227.90	12.301%	$255.934	$255.93	$255.95	$255.90
Purchase #6	$121.51	13.376%	$137.7632	$137.76	$137.75	$137.80
Purchase #7	$195.67	11.731%	$218.624	$218.62	$218.60	$218.60
7 purchase totals =	$906.92		$1,016.3712	$1,016.35	$1,016.35	$1,016.40