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	$104.65	3.457%	$108.2678	$108.27	$108.25	$108.30
Purchase #2	$80.48	3.420%	$83.2324	$83.23	$83.25	$83.20
Purchase #3	$85.43	11.795%	$95.5065	$95.51	$95.50	$95.50
Purchase #4	$109.62	4.110%	$114.1254	$114.13	$114.15	$114.10
Purchase #5	$170.98	3.466%	$176.9062	$176.91	$176.90	$176.90
Purchase #6	$160.73	11.684%	$179.5097	$179.51	$179.50	$179.50
Purchase #7	$196.61	8.579%	$213.4772	$213.48	$213.50	$213.50
7 purchase totals =	$908.50		$971.0252	$971.04	$971.05	$971.00