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	$20.55	8.609%	$22.3191	$22.32	$22.30	$22.30
Purchase #2	$79.61	3.781%	$82.6201	$82.62	$82.60	$82.60
Purchase #3	$85.70	11.430%	$95.4955	$95.50	$95.50	$95.50
Purchase #4	$210.32	6.213%	$223.3872	$223.39	$223.40	$223.40
Purchase #5	$179.75	5.643%	$189.8933	$189.89	$189.90	$189.90
Purchase #6	$124.52	11.163%	$138.4202	$138.42	$138.40	$138.40
Purchase #7	$208.26	3.526%	$215.6032	$215.60	$215.60	$215.60
7 purchase totals =	$908.71		$967.7386	$967.74	$967.70	$967.70