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	$201.27	8.169%	$217.7117	$217.71	$217.70	$217.70
Purchase #2	$172.72	4.145%	$179.8792	$179.88	$179.90	$179.90
Purchase #3	$164.45	6.337%	$174.8712	$174.87	$174.85	$174.90
Purchase #4	$123.80	7.396%	$132.9562	$132.96	$132.95	$133.00
Purchase #5	$83.53	4.165%	$87.009	$87.01	$87.00	$87.00
Purchase #6	$152.41	5.260%	$160.4268	$160.43	$160.45	$160.40
Purchase #7	$131.34	12.207%	$147.3727	$147.37	$147.35	$147.40
7 purchase totals =	$1,029.52		$1,100.2268	$1,100.23	$1,100.20	$1,100.30