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	$219.63	5.580%	$231.8854	$231.89	$231.90	$231.90
Purchase #2	$59.39	10.367%	$65.547	$65.55	$65.55	$65.50
Purchase #3	$159.74	11.141%	$177.5366	$177.54	$177.55	$177.50
Purchase #4	$182.83	7.421%	$196.3978	$196.40	$196.40	$196.40
Purchase #5	$147.65	5.104%	$155.1861	$155.19	$155.20	$155.20
Purchase #6	$224.56	8.433%	$243.4971	$243.50	$243.50	$243.50
Purchase #7	$172.86	12.629%	$194.6905	$194.69	$194.70	$194.70
7 purchase totals =	$1,166.66		$1,264.7405	$1,264.76	$1,264.80	$1,264.70