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	$53.65	11.112%	$59.6116	$59.61	$59.60	$59.60
Purchase #2	$112.94	9.703%	$123.8986	$123.90	$123.90	$123.90
Purchase #3	$156.61	7.461%	$168.2947	$168.29	$168.30	$168.30
Purchase #4	$72.37	8.663%	$78.6394	$78.64	$78.65	$78.60
Purchase #5	$218.30	8.514%	$236.8861	$236.89	$236.90	$236.90
Purchase #6	$9.67	5.350%	$10.1873	$10.19	$10.20	$10.20
Purchase #7	$234.65	10.845%	$260.0978	$260.10	$260.10	$260.10
7 purchase totals =	$858.19		$937.6155	$937.62	$937.65	$937.60