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	$58.81	10.290%	$64.8615	$64.86	$64.85	$64.90
Purchase #2	$80.63	7.366%	$86.5692	$86.57	$86.55	$86.60
Purchase #3	$208.87	5.492%	$220.3411	$220.34	$220.35	$220.30
Purchase #4	$53.85	13.511%	$61.1257	$61.13	$61.15	$61.10
Purchase #5	$66.67	8.322%	$72.2183	$72.22	$72.20	$72.20
Purchase #6	$78.82	12.697%	$88.8278	$88.83	$88.85	$88.80
Purchase #7	$120.83	10.833%	$133.9195	$133.92	$133.90	$133.90
7 purchase totals =	$668.48		$727.8631	$727.87	$727.85	$727.80