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	$190.27	13.466%	$215.8918	$215.89	$215.90	$215.90
Purchase #2	$133.36	3.378%	$137.8649	$137.86	$137.85	$137.90
Purchase #3	$133.97	10.580%	$148.144	$148.14	$148.15	$148.10
Purchase #4	$29.65	6.503%	$31.5781	$31.58	$31.60	$31.60
Purchase #5	$243.46	8.522%	$264.2077	$264.21	$264.20	$264.20
Purchase #6	$208.35	3.837%	$216.3444	$216.34	$216.35	$216.30
Purchase #7	$64.26	12.396%	$72.2257	$72.23	$72.25	$72.20
7 purchase totals =	$1,003.32		$1,086.2566	$1,086.25	$1,086.30	$1,086.20