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	$161.78	6.378%	$172.0983	$172.10	$172.10	$172.10
Purchase #2	$198.35	8.253%	$214.7198	$214.72	$214.70	$214.70
Purchase #3	$90.29	8.548%	$98.008	$98.01	$98.00	$98.00
Purchase #4	$213.82	5.647%	$225.8944	$225.89	$225.90	$225.90
Purchase #5	$159.44	3.178%	$164.507	$164.51	$164.50	$164.50
Purchase #6	$95.43	3.215%	$98.4981	$98.50	$98.50	$98.50
Purchase #7	$232.64	13.555%	$264.1744	$264.17	$264.15	$264.20
7 purchase totals =	$1,151.75		$1,237.9000	$1,237.90	$1,237.85	$1,237.90