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	$65.53	5.145%	$68.9015	$68.90	$68.90	$68.90
Purchase #2	$79.34	5.223%	$83.4839	$83.48	$83.50	$83.50
Purchase #3	$237.61	12.319%	$266.8812	$266.88	$266.90	$266.90
Purchase #4	$126.67	12.316%	$142.2707	$142.27	$142.25	$142.30
Purchase #5	$159.28	3.808%	$165.3454	$165.35	$165.35	$165.30
Purchase #6	$208.53	13.418%	$236.5106	$236.51	$236.50	$236.50
Purchase #7	$151.42	13.213%	$171.4271	$171.43	$171.45	$171.40
7 purchase totals =	$1,028.38		$1,134.8204	$1,134.82	$1,134.85	$1,134.80