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	$152.87	5.829%	$161.7808	$161.78	$161.80	$161.80
Purchase #2	$87.67	12.658%	$98.7673	$98.77	$98.75	$98.80
Purchase #3	$111.36	7.341%	$119.5349	$119.53	$119.55	$119.50
Purchase #4	$98.77	13.282%	$111.8886	$111.89	$111.90	$111.90
Purchase #5	$93.61	7.108%	$100.2638	$100.26	$100.25	$100.30
Purchase #6	$171.76	9.181%	$187.5293	$187.53	$187.55	$187.50
Purchase #7	$88.80	7.551%	$95.5053	$95.51	$95.50	$95.50
7 purchase totals =	$804.84		$875.2700	$875.27	$875.30	$875.30