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	$222.83	5.355%	$234.7625	$234.76	$234.75	$234.80
Purchase #2	$48.78	5.591%	$51.5073	$51.51	$51.50	$51.50
Purchase #3	$76.90	11.861%	$86.0211	$86.02	$86.00	$86.00
Purchase #4	$111.62	8.294%	$120.8778	$120.88	$120.90	$120.90
Purchase #5	$59.89	5.712%	$63.3109	$63.31	$63.30	$63.30
Purchase #6	$204.86	3.739%	$212.5197	$212.52	$212.50	$212.50
Purchase #7	$81.47	7.389%	$87.4898	$87.49	$87.50	$87.50
7 purchase totals =	$806.35		$856.4891	$856.49	$856.45	$856.50