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	$132.77	3.822%	$137.8445	$137.84	$137.85	$137.80
Purchase #2	$126.44	4.103%	$131.6278	$131.63	$131.65	$131.60
Purchase #3	$185.74	12.290%	$208.5674	$208.57	$208.55	$208.60
Purchase #4	$190.27	11.243%	$211.6621	$211.66	$211.65	$211.70
Purchase #5	$145.48	7.645%	$156.6019	$156.60	$156.60	$156.60
Purchase #6	$171.60	7.712%	$184.8338	$184.83	$184.85	$184.80
Purchase #7	$22.97	10.695%	$25.4266	$25.43	$25.45	$25.40
7 purchase totals =	$975.27		$1,056.5641	$1,056.56	$1,056.60	$1,056.50