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	$172.30	4.639%	$180.293	$180.29	$180.30	$180.30
Purchase #2	$84.68	8.683%	$92.0328	$92.03	$92.05	$92.00
Purchase #3	$161.25	13.726%	$183.3832	$183.38	$183.40	$183.40
Purchase #4	$55.57	7.799%	$59.9039	$59.90	$59.90	$59.90
Purchase #5	$85.94	3.751%	$89.1636	$89.16	$89.15	$89.20
Purchase #6	$141.61	7.383%	$152.0651	$152.07	$152.05	$152.10
Purchase #7	$184.38	3.483%	$190.802	$190.80	$190.80	$190.80
7 purchase totals =	$885.73		$947.6436	$947.63	$947.65	$947.70