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	$187.37	13.818%	$213.2608	$213.26	$213.25	$213.30
Purchase #2	$12.57	11.102%	$13.9655	$13.97	$13.95	$14.00
Purchase #3	$166.34	9.636%	$182.3685	$182.37	$182.35	$182.40
Purchase #4	$159.27	3.444%	$164.7553	$164.76	$164.75	$164.80
Purchase #5	$83.46	7.103%	$89.3882	$89.39	$89.40	$89.40
Purchase #6	$109.77	6.124%	$116.4923	$116.49	$116.50	$116.50
Purchase #7	$137.81	13.605%	$156.5591	$156.56	$156.55	$156.60
7 purchase totals =	$856.59		$936.7897	$936.80	$936.75	$937.00