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	$171.69	10.772%	$190.1844	$190.18	$190.20	$190.20
Purchase #2	$73.56	13.533%	$83.5149	$83.51	$83.50	$83.50
Purchase #3	$93.84	7.713%	$101.0779	$101.08	$101.10	$101.10
Purchase #4	$182.48	3.233%	$188.3796	$188.38	$188.40	$188.40
Purchase #5	$47.71	10.134%	$52.5449	$52.54	$52.55	$52.50
Purchase #6	$37.77	6.838%	$40.3527	$40.35	$40.35	$40.40
Purchase #7	$150.77	6.848%	$161.0947	$161.09	$161.10	$161.10
7 purchase totals =	$757.82		$817.1491	$817.13	$817.20	$817.20