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	$103.86	8.688%	$112.8834	$112.88	$112.90	$112.90
Purchase #2	$129.38	6.110%	$137.2851	$137.29	$137.30	$137.30
Purchase #3	$35.52	12.127%	$39.8275	$39.83	$39.85	$39.80
Purchase #4	$213.28	4.166%	$222.1652	$222.17	$222.15	$222.20
Purchase #5	$70.99	6.612%	$75.6839	$75.68	$75.70	$75.70
Purchase #6	$95.69	5.357%	$100.8161	$100.82	$100.80	$100.80
Purchase #7	$226.99	7.119%	$243.1494	$243.15	$243.15	$243.10
7 purchase totals =	$875.71		$931.8106	$931.82	$931.85	$931.80