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	$111.32	3.576%	$115.3008	$115.30	$115.30	$115.30
Purchase #2	$135.37	3.252%	$139.7722	$139.77	$139.75	$139.80
Purchase #3	$177.66	10.409%	$196.1526	$196.15	$196.15	$196.20
Purchase #4	$123.72	12.813%	$139.5722	$139.57	$139.55	$139.60
Purchase #5	$213.42	9.584%	$233.8742	$233.87	$233.85	$233.90
Purchase #6	$171.66	6.804%	$183.3397	$183.34	$183.35	$183.30
Purchase #7	$64.36	6.126%	$68.3027	$68.30	$68.30	$68.30
7 purchase totals =	$997.51		$1,076.3144	$1,076.30	$1,076.25	$1,076.40