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	$67.80	6.297%	$72.0694	$72.07	$72.05	$72.10
Purchase #2	$54.60	3.651%	$56.5934	$56.59	$56.60	$56.60
Purchase #3	$235.80	3.647%	$244.3996	$244.40	$244.40	$244.40
Purchase #4	$118.52	4.523%	$123.8807	$123.88	$123.90	$123.90
Purchase #5	$155.53	9.196%	$169.8325	$169.83	$169.85	$169.80
Purchase #6	$95.32	11.620%	$106.3962	$106.40	$106.40	$106.40
Purchase #7	$139.84	9.549%	$153.1933	$153.19	$153.20	$153.20
7 purchase totals =	$867.41		$926.3651	$926.36	$926.40	$926.40