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	$217.34	13.400%	$246.4636	$246.46	$246.45	$246.50
Purchase #2	$87.86	3.225%	$90.6935	$90.69	$90.70	$90.70
Purchase #3	$175.42	11.752%	$196.0354	$196.04	$196.05	$196.00
Purchase #4	$81.58	10.366%	$90.0366	$90.04	$90.05	$90.00
Purchase #5	$50.25	13.414%	$56.9905	$56.99	$57.00	$57.00
Purchase #6	$229.71	4.724%	$240.5615	$240.56	$240.55	$240.60
Purchase #7	$184.82	3.840%	$191.9171	$191.92	$191.90	$191.90
7 purchase totals =	$1,026.98		$1,112.6982	$1,112.70	$1,112.70	$1,112.70