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	$187.77	4.729%	$196.6496	$196.65	$196.65	$196.60
Purchase #2	$119.57	6.456%	$127.2894	$127.29	$127.30	$127.30
Purchase #3	$214.66	10.183%	$236.5188	$236.52	$236.50	$236.50
Purchase #4	$224.53	3.785%	$233.0285	$233.03	$233.05	$233.00
Purchase #5	$67.51	5.676%	$71.3419	$71.34	$71.35	$71.30
Purchase #6	$234.83	11.187%	$261.1004	$261.10	$261.10	$261.10
Purchase #7	$177.28	3.187%	$182.9299	$182.93	$182.95	$182.90
7 purchase totals =	$1,226.15		$1,308.8585	$1,308.86	$1,308.90	$1,308.70