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	$57.87	6.139%	$61.4226	$61.42	$61.40	$61.40
Purchase #2	$66.70	11.779%	$74.5566	$74.56	$74.55	$74.60
Purchase #3	$88.34	9.149%	$96.4222	$96.42	$96.40	$96.40
Purchase #4	$74.59	10.714%	$82.5816	$82.58	$82.60	$82.60
Purchase #5	$247.25	9.687%	$271.2011	$271.20	$271.20	$271.20
Purchase #6	$118.59	10.684%	$131.2602	$131.26	$131.25	$131.30
Purchase #7	$42.36	4.844%	$44.4119	$44.41	$44.40	$44.40
7 purchase totals =	$695.70		$761.8562	$761.85	$761.80	$761.90