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	$187.43	11.274%	$208.5609	$208.56	$208.55	$208.60
Purchase #2	$90.48	3.377%	$93.5355	$93.54	$93.55	$93.50
Purchase #3	$47.89	9.472%	$52.4261	$52.43	$52.45	$52.40
Purchase #4	$228.25	13.483%	$259.0249	$259.02	$259.00	$259.00
Purchase #5	$224.39	10.755%	$248.5231	$248.52	$248.50	$248.50
Purchase #6	$75.87	10.548%	$83.8728	$83.87	$83.85	$83.90
Purchase #7	$94.88	10.158%	$104.5179	$104.52	$104.50	$104.50
7 purchase totals =	$949.19		$1,050.4612	$1,050.46	$1,050.40	$1,050.40