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	$228.77	12.233%	$256.7554	$256.76	$256.75	$256.80
Purchase #2	$143.83	13.303%	$162.9637	$162.96	$162.95	$163.00
Purchase #3	$54.82	3.592%	$56.7891	$56.79	$56.80	$56.80
Purchase #4	$29.61	6.318%	$31.4808	$31.48	$31.50	$31.50
Purchase #5	$179.90	5.614%	$189.9996	$190.00	$190.00	$190.00
Purchase #6	$191.26	12.551%	$215.265	$215.27	$215.25	$215.30
Purchase #7	$237.31	7.145%	$254.2658	$254.27	$254.25	$254.30
7 purchase totals =	$1,065.50		$1,167.5194	$1,167.53	$1,167.50	$1,167.70