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	$92.47	13.427%	$104.8859	$104.89	$104.90	$104.90
Purchase #2	$156.53	7.649%	$168.503	$168.50	$168.50	$168.50
Purchase #3	$134.62	13.519%	$152.8193	$152.82	$152.80	$152.80
Purchase #4	$57.90	12.403%	$65.0813	$65.08	$65.10	$65.10
Purchase #5	$158.90	13.842%	$180.8949	$180.89	$180.90	$180.90
Purchase #6	$157.29	8.787%	$171.1111	$171.11	$171.10	$171.10
Purchase #7	$185.34	5.387%	$195.3243	$195.32	$195.30	$195.30
7 purchase totals =	$943.05		$1,038.6198	$1,038.61	$1,038.60	$1,038.60