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	$190.67	12.204%	$213.9394	$213.94	$213.95	$213.90
Purchase #2	$51.96	4.703%	$54.4037	$54.40	$54.40	$54.40
Purchase #3	$86.58	4.320%	$90.3203	$90.32	$90.30	$90.30
Purchase #4	$135.32	9.582%	$148.2864	$148.29	$148.30	$148.30
Purchase #5	$199.63	3.512%	$206.641	$206.64	$206.65	$206.60
Purchase #6	$54.31	7.483%	$58.374	$58.37	$58.35	$58.40
Purchase #7	$132.75	3.654%	$137.6007	$137.60	$137.60	$137.60
7 purchase totals =	$851.22		$909.5655	$909.56	$909.55	$909.50