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	$245.91	11.629%	$274.5069	$274.51	$274.50	$274.50
Purchase #2	$12.73	4.864%	$13.3492	$13.35	$13.35	$13.30
Purchase #3	$188.79	8.630%	$205.0826	$205.08	$205.10	$205.10
Purchase #4	$95.85	4.508%	$100.1709	$100.17	$100.15	$100.20
Purchase #5	$56.88	8.538%	$61.7364	$61.74	$61.75	$61.70
Purchase #6	$109.40	9.552%	$119.8499	$119.85	$119.85	$119.80
Purchase #7	$207.61	12.862%	$234.3128	$234.31	$234.30	$234.30
7 purchase totals =	$917.17		$1,009.0087	$1,009.01	$1,009.00	$1,008.90