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	$82.37	3.796%	$85.4968	$85.50	$85.50	$85.50
Purchase #2	$45.34	5.533%	$47.8487	$47.85	$47.85	$47.80
Purchase #3	$223.43	4.685%	$233.8977	$233.90	$233.90	$233.90
Purchase #4	$52.65	3.664%	$54.5791	$54.58	$54.60	$54.60
Purchase #5	$206.66	12.267%	$232.011	$232.01	$232.00	$232.00
Purchase #6	$225.98	12.669%	$254.6094	$254.61	$254.60	$254.60
Purchase #7	$145.99	3.447%	$151.0223	$151.02	$151.00	$151.00
7 purchase totals =	$982.42		$1,059.4650	$1,059.47	$1,059.45	$1,059.40