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	$117.64	12.119%	$131.8968	$131.90	$131.90	$131.90
Purchase #2	$243.45	7.226%	$261.0417	$261.04	$261.05	$261.00
Purchase #3	$37.75	12.451%	$42.4503	$42.45	$42.45	$42.50
Purchase #4	$219.99	6.212%	$233.6558	$233.66	$233.65	$233.70
Purchase #5	$6.40	7.138%	$6.8568	$6.86	$6.85	$6.90
Purchase #6	$98.45	4.270%	$102.6538	$102.65	$102.65	$102.70
Purchase #7	$209.39	11.592%	$233.6625	$233.66	$233.65	$233.70
7 purchase totals =	$933.07		$1,012.2177	$1,012.22	$1,012.20	$1,012.40