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	$213.56	13.490%	$242.3692	$242.37	$242.35	$242.40
Purchase #2	$203.55	9.310%	$222.5005	$222.50	$222.50	$222.50
Purchase #3	$105.82	11.391%	$117.874	$117.87	$117.85	$117.90
Purchase #4	$178.33	9.178%	$194.6971	$194.70	$194.70	$194.70
Purchase #5	$179.93	4.431%	$187.9027	$187.90	$187.90	$187.90
Purchase #6	$46.56	10.738%	$51.5596	$51.56	$51.55	$51.60
Purchase #7	$13.55	3.769%	$14.0607	$14.06	$14.05	$14.10
7 purchase totals =	$941.30		$1,030.9638	$1,030.96	$1,030.90	$1,031.10