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	$177.89	5.541%	$187.7469	$187.75	$187.75	$187.70
Purchase #2	$24.89	12.267%	$27.9433	$27.94	$27.95	$27.90
Purchase #3	$42.51	11.623%	$47.4509	$47.45	$47.45	$47.50
Purchase #4	$35.45	6.553%	$37.773	$37.77	$37.75	$37.80
Purchase #5	$86.48	3.786%	$89.7541	$89.75	$89.75	$89.80
Purchase #6	$89.40	13.783%	$101.722	$101.72	$101.70	$101.70
Purchase #7	$171.59	10.693%	$189.9381	$189.94	$189.95	$189.90
7 purchase totals =	$628.21		$682.3283	$682.32	$682.30	$682.30