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	$211.94	11.518%	$236.3512	$236.35	$236.35	$236.40
Purchase #2	$58.65	6.638%	$62.5432	$62.54	$62.55	$62.50
Purchase #3	$54.49	10.405%	$60.1597	$60.16	$60.15	$60.20
Purchase #4	$9.34	7.493%	$10.0398	$10.04	$10.05	$10.00
Purchase #5	$185.37	5.738%	$196.0065	$196.01	$196.00	$196.00
Purchase #6	$243.72	12.354%	$273.8292	$273.83	$273.85	$273.80
Purchase #7	$96.66	3.677%	$100.2142	$100.21	$100.20	$100.20
7 purchase totals =	$860.17		$939.1438	$939.14	$939.15	$939.10