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	$226.93	10.550%	$250.8711	$250.87	$250.85	$250.90
Purchase #2	$98.57	10.651%	$109.0687	$109.07	$109.05	$109.10
Purchase #3	$220.74	8.134%	$238.695	$238.70	$238.70	$238.70
Purchase #4	$90.79	6.617%	$96.7976	$96.80	$96.80	$96.80
Purchase #5	$247.48	13.388%	$280.6126	$280.61	$280.60	$280.60
Purchase #6	$91.48	7.747%	$98.567	$98.57	$98.55	$98.60
Purchase #7	$123.90	10.643%	$137.0867	$137.09	$137.10	$137.10
7 purchase totals =	$1,099.89		$1,211.6987	$1,211.71	$1,211.65	$1,211.80