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	$216.89	4.192%	$225.982	$225.98	$226.00	$226.00
Purchase #2	$192.53	7.400%	$206.7772	$206.78	$206.80	$206.80
Purchase #3	$89.34	12.442%	$100.4557	$100.46	$100.45	$100.50
Purchase #4	$160.49	8.388%	$173.9519	$173.95	$173.95	$174.00
Purchase #5	$109.32	9.175%	$119.3501	$119.35	$119.35	$119.40
Purchase #6	$201.58	10.325%	$222.3931	$222.39	$222.40	$222.40
Purchase #7	$40.85	7.609%	$43.9583	$43.96	$43.95	$44.00
7 purchase totals =	$1,011.00		$1,092.8683	$1,092.87	$1,092.90	$1,093.10