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	$84.67	10.629%	$93.6696	$93.67	$93.65	$93.70
Purchase #2	$51.75	3.344%	$53.4805	$53.48	$53.50	$53.50
Purchase #3	$165.60	13.820%	$188.4859	$188.49	$188.50	$188.50
Purchase #4	$156.28	10.422%	$172.5675	$172.57	$172.55	$172.60
Purchase #5	$77.65	6.360%	$82.5885	$82.59	$82.60	$82.60
Purchase #6	$30.49	13.237%	$34.526	$34.53	$34.55	$34.50
Purchase #7	$110.88	8.696%	$120.5221	$120.52	$120.50	$120.50
7 purchase totals =	$677.32		$745.8401	$745.85	$745.85	$745.90