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	$117.85	11.241%	$131.0975	$131.10	$131.10	$131.10
Purchase #2	$150.46	6.249%	$159.8622	$159.86	$159.85	$159.90
Purchase #3	$189.99	3.339%	$196.3338	$196.33	$196.35	$196.30
Purchase #4	$188.89	7.868%	$203.7519	$203.75	$203.75	$203.80
Purchase #5	$156.95	4.537%	$164.0708	$164.07	$164.05	$164.10
Purchase #6	$24.88	13.676%	$28.2826	$28.28	$28.30	$28.30
Purchase #7	$180.38	3.105%	$185.9808	$185.98	$186.00	$186.00
7 purchase totals =	$1,009.40		$1,069.3796	$1,069.37	$1,069.40	$1,069.50