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	$161.34	4.398%	$168.4357	$168.44	$168.45	$168.40
Purchase #2	$40.36	9.703%	$44.2761	$44.28	$44.30	$44.30
Purchase #3	$131.56	4.123%	$136.9842	$136.98	$137.00	$137.00
Purchase #4	$54.38	5.834%	$57.5525	$57.55	$57.55	$57.60
Purchase #5	$75.96	3.719%	$78.785	$78.79	$78.80	$78.80
Purchase #6	$84.67	5.561%	$89.3785	$89.38	$89.40	$89.40
Purchase #7	$168.99	3.293%	$174.5548	$174.55	$174.55	$174.60
7 purchase totals =	$717.26		$749.9668	$749.97	$750.05	$750.10