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	$93.54	9.814%	$102.72	$102.72	$102.70	$102.70
Purchase #2	$219.52	3.187%	$226.5161	$226.52	$226.50	$226.50
Purchase #3	$86.80	8.659%	$94.316	$94.32	$94.30	$94.30
Purchase #4	$25.95	6.135%	$27.542	$27.54	$27.55	$27.50
Purchase #5	$134.35	10.102%	$147.922	$147.92	$147.90	$147.90
Purchase #6	$78.67	4.708%	$82.3738	$82.37	$82.35	$82.40
Purchase #7	$48.77	11.666%	$54.4595	$54.46	$54.45	$54.50
7 purchase totals =	$687.60		$735.8494	$735.85	$735.75	$735.80