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	$131.86	4.526%	$137.828	$137.83	$137.85	$137.80
Purchase #2	$212.82	9.125%	$232.2398	$232.24	$232.25	$232.20
Purchase #3	$43.29	13.807%	$49.2671	$49.27	$49.25	$49.30
Purchase #4	$193.82	3.653%	$200.9002	$200.90	$200.90	$200.90
Purchase #5	$81.27	6.306%	$86.3949	$86.39	$86.40	$86.40
Purchase #6	$179.70	5.735%	$190.0058	$190.01	$190.00	$190.00
Purchase #7	$160.84	7.405%	$172.7502	$172.75	$172.75	$172.80
7 purchase totals =	$1,003.60		$1,069.3860	$1,069.39	$1,069.40	$1,069.40