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	$127.54	5.768%	$134.8965	$134.90	$134.90	$134.90
Purchase #2	$108.38	3.361%	$112.0227	$112.02	$112.00	$112.00
Purchase #3	$208.66	6.725%	$222.6924	$222.69	$222.70	$222.70
Purchase #4	$111.36	7.625%	$119.8512	$119.85	$119.85	$119.90
Purchase #5	$206.93	7.725%	$222.9153	$222.92	$222.90	$222.90
Purchase #6	$216.33	12.760%	$243.9337	$243.93	$243.95	$243.90
Purchase #7	$39.80	12.449%	$44.7547	$44.75	$44.75	$44.80
7 purchase totals =	$1,019.00		$1,101.0665	$1,101.06	$1,101.05	$1,101.10