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	$144.27	7.325%	$154.8378	$154.84	$154.85	$154.80
Purchase #2	$215.27	5.465%	$227.0345	$227.03	$227.05	$227.00
Purchase #3	$79.74	12.743%	$89.9013	$89.90	$89.90	$89.90
Purchase #4	$150.59	3.262%	$155.5022	$155.50	$155.50	$155.50
Purchase #5	$186.85	12.861%	$210.8808	$210.88	$210.90	$210.90
Purchase #6	$80.59	5.425%	$84.962	$84.96	$84.95	$85.00
Purchase #7	$73.71	3.224%	$76.0864	$76.09	$76.10	$76.10
7 purchase totals =	$931.02		$999.2050	$999.20	$999.25	$999.20