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	$114.28	7.480%	$122.8281	$122.83	$122.85	$122.80
Purchase #2	$104.96	7.109%	$112.4216	$112.42	$112.40	$112.40
Purchase #3	$90.55	13.677%	$102.9345	$102.93	$102.95	$102.90
Purchase #4	$181.73	9.421%	$198.8508	$198.85	$198.85	$198.90
Purchase #5	$249.48	12.505%	$280.6775	$280.68	$280.70	$280.70
Purchase #6	$194.80	11.576%	$217.35	$217.35	$217.35	$217.40
Purchase #7	$100.91	8.298%	$109.2835	$109.28	$109.30	$109.30
7 purchase totals =	$1,036.71		$1,144.3460	$1,144.34	$1,144.40	$1,144.40