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	$193.43	13.460%	$219.4657	$219.47	$219.45	$219.50
Purchase #2	$33.77	13.588%	$38.3587	$38.36	$38.35	$38.40
Purchase #3	$196.47	13.261%	$222.5239	$222.52	$222.50	$222.50
Purchase #4	$147.96	10.836%	$163.9929	$163.99	$164.00	$164.00
Purchase #5	$236.46	11.173%	$262.8797	$262.88	$262.90	$262.90
Purchase #6	$176.46	11.562%	$196.8623	$196.86	$196.85	$196.90
Purchase #7	$222.98	6.293%	$237.0121	$237.01	$237.00	$237.00
7 purchase totals =	$1,207.53		$1,341.0953	$1,341.09	$1,341.05	$1,341.20