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	$132.91	11.536%	$148.2425	$148.24	$148.25	$148.20
Purchase #2	$201.74	12.168%	$226.2877	$226.29	$226.30	$226.30
Purchase #3	$13.78	7.660%	$14.8355	$14.84	$14.85	$14.80
Purchase #4	$66.74	9.155%	$72.85	$72.85	$72.85	$72.90
Purchase #5	$131.48	9.673%	$144.1981	$144.20	$144.20	$144.20
Purchase #6	$162.76	11.704%	$181.8094	$181.81	$181.80	$181.80
Purchase #7	$147.53	3.428%	$152.5873	$152.59	$152.60	$152.60
7 purchase totals =	$856.94		$940.8105	$940.82	$940.85	$940.80