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	$59.31	4.371%	$61.9024	$61.90	$61.90	$61.90
Purchase #2	$58.93	5.706%	$62.2925	$62.29	$62.30	$62.30
Purchase #3	$218.38	11.513%	$243.5221	$243.52	$243.50	$243.50
Purchase #4	$167.95	5.677%	$177.4845	$177.48	$177.50	$177.50
Purchase #5	$22.90	10.497%	$25.3038	$25.30	$25.30	$25.30
Purchase #6	$239.89	3.602%	$248.5308	$248.53	$248.55	$248.50
Purchase #7	$84.72	13.610%	$96.2504	$96.25	$96.25	$96.30
7 purchase totals =	$852.08		$915.2865	$915.27	$915.30	$915.30