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	$93.32	12.829%	$105.292	$105.29	$105.30	$105.30
Purchase #2	$89.54	13.467%	$101.5984	$101.60	$101.60	$101.60
Purchase #3	$162.39	4.612%	$169.8794	$169.88	$169.90	$169.90
Purchase #4	$25.47	9.476%	$27.8835	$27.88	$27.90	$27.90
Purchase #5	$81.70	7.423%	$87.7646	$87.76	$87.75	$87.80
Purchase #6	$152.81	10.517%	$168.881	$168.88	$168.90	$168.90
Purchase #7	$223.78	12.416%	$251.5645	$251.56	$251.55	$251.60
7 purchase totals =	$829.01		$912.8634	$912.85	$912.90	$913.00