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	$218.96	13.645%	$248.8371	$248.84	$248.85	$248.80
Purchase #2	$6.50	12.634%	$7.3212	$7.32	$7.30	$7.30
Purchase #3	$203.75	11.516%	$227.2139	$227.21	$227.20	$227.20
Purchase #4	$70.62	3.256%	$72.9194	$72.92	$72.90	$72.90
Purchase #5	$213.49	7.423%	$229.3374	$229.34	$229.35	$229.30
Purchase #6	$197.27	9.216%	$215.4504	$215.45	$215.45	$215.50
Purchase #7	$82.82	6.681%	$88.3532	$88.35	$88.35	$88.40
7 purchase totals =	$993.41		$1,089.4326	$1,089.43	$1,089.40	$1,089.40