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	$90.50	6.272%	$96.1762	$96.18	$96.20	$96.20
Purchase #2	$174.57	7.614%	$187.8618	$187.86	$187.85	$187.90
Purchase #3	$72.87	13.490%	$82.7002	$82.70	$82.70	$82.70
Purchase #4	$38.98	6.390%	$41.4708	$41.47	$41.45	$41.50
Purchase #5	$218.94	8.368%	$237.2609	$237.26	$237.25	$237.30
Purchase #6	$139.51	5.291%	$146.8915	$146.89	$146.90	$146.90
Purchase #7	$193.52	12.289%	$217.3017	$217.30	$217.30	$217.30
7 purchase totals =	$928.89		$1,009.6631	$1,009.66	$1,009.65	$1,009.80