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	$31.42	5.119%	$33.0284	$33.03	$33.05	$33.00
Purchase #2	$82.39	4.610%	$86.1882	$86.19	$86.20	$86.20
Purchase #3	$245.86	13.810%	$279.8133	$279.81	$279.80	$279.80
Purchase #4	$130.98	8.539%	$142.1644	$142.16	$142.15	$142.20
Purchase #5	$90.60	6.228%	$96.2426	$96.24	$96.25	$96.20
Purchase #6	$45.82	5.538%	$48.3575	$48.36	$48.35	$48.40
Purchase #7	$222.39	9.789%	$244.1598	$244.16	$244.15	$244.20
7 purchase totals =	$849.46		$929.9542	$929.95	$929.95	$930.00