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	$132.95	6.730%	$141.8975	$141.90	$141.90	$141.90
Purchase #2	$243.80	12.344%	$273.8947	$273.89	$273.90	$273.90
Purchase #3	$74.83	11.856%	$83.7018	$83.70	$83.70	$83.70
Purchase #4	$218.59	9.228%	$238.7615	$238.76	$238.75	$238.80
Purchase #5	$39.60	5.686%	$41.8517	$41.85	$41.85	$41.90
Purchase #6	$168.67	10.730%	$186.7683	$186.77	$186.75	$186.80
Purchase #7	$152.78	11.626%	$170.5422	$170.54	$170.55	$170.50
7 purchase totals =	$1,031.22		$1,137.4177	$1,137.41	$1,137.40	$1,137.50