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	$53.36	4.215%	$55.6091	$55.61	$55.60	$55.60
Purchase #2	$10.73	7.343%	$11.5179	$11.52	$11.50	$11.50
Purchase #3	$17.73	5.593%	$18.7216	$18.72	$18.70	$18.70
Purchase #4	$125.82	12.317%	$141.3172	$141.32	$141.30	$141.30
Purchase #5	$187.52	11.623%	$209.3154	$209.32	$209.30	$209.30
Purchase #6	$111.69	4.321%	$116.5161	$116.52	$116.50	$116.50
Purchase #7	$112.86	7.822%	$121.6879	$121.69	$121.70	$121.70
7 purchase totals =	$619.71		$674.6852	$674.70	$674.60	$674.60