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	$31.65	4.838%	$33.1812	$33.18	$33.20	$33.20
Purchase #2	$63.82	7.440%	$68.5682	$68.57	$68.55	$68.60
Purchase #3	$102.70	6.849%	$109.7339	$109.73	$109.75	$109.70
Purchase #4	$240.45	6.305%	$255.6104	$255.61	$255.60	$255.60
Purchase #5	$172.35	13.572%	$195.7413	$195.74	$195.75	$195.70
Purchase #6	$89.82	13.870%	$102.278	$102.28	$102.30	$102.30
Purchase #7	$213.93	4.123%	$222.7503	$222.75	$222.75	$222.80
7 purchase totals =	$914.72		$987.8633	$987.86	$987.90	$987.90