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	$6.97	13.619%	$7.9192	$7.92	$7.90	$7.90
Purchase #2	$193.51	3.132%	$199.5707	$199.57	$199.55	$199.60
Purchase #3	$202.88	3.290%	$209.5548	$209.55	$209.55	$209.60
Purchase #4	$211.66	12.340%	$237.7788	$237.78	$237.80	$237.80
Purchase #5	$35.92	13.788%	$40.8726	$40.87	$40.85	$40.90
Purchase #6	$173.32	13.581%	$196.8586	$196.86	$196.85	$196.90
Purchase #7	$142.46	7.637%	$153.3397	$153.34	$153.35	$153.30
7 purchase totals =	$966.72		$1,045.8944	$1,045.89	$1,045.85	$1,046.00