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	$52.34	7.557%	$56.2953	$56.30	$56.30	$56.30
Purchase #2	$43.44	3.462%	$44.9439	$44.94	$44.95	$44.90
Purchase #3	$112.50	10.234%	$124.0133	$124.01	$124.00	$124.00
Purchase #4	$140.54	8.489%	$152.4704	$152.47	$152.45	$152.50
Purchase #5	$128.48	13.228%	$145.4753	$145.48	$145.50	$145.50
Purchase #6	$232.81	13.605%	$264.4838	$264.48	$264.50	$264.50
Purchase #7	$113.84	11.176%	$126.5628	$126.56	$126.55	$126.60
7 purchase totals =	$823.95		$914.2448	$914.24	$914.25	$914.30