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	$81.73	11.172%	$90.8609	$90.86	$90.85	$90.90
Purchase #2	$131.36	12.231%	$147.4266	$147.43	$147.45	$147.40
Purchase #3	$152.76	9.645%	$167.4937	$167.49	$167.50	$167.50
Purchase #4	$7.53	5.442%	$7.9398	$7.94	$7.95	$7.90
Purchase #5	$49.87	8.742%	$54.2296	$54.23	$54.25	$54.20
Purchase #6	$161.99	3.277%	$167.2984	$167.30	$167.30	$167.30
Purchase #7	$102.45	13.802%	$116.5901	$116.59	$116.60	$116.60
7 purchase totals =	$687.69		$751.8391	$751.84	$751.90	$751.80