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	$31.71	6.762%	$33.8542	$33.85	$33.85	$33.90
Purchase #2	$225.43	7.538%	$242.4229	$242.42	$242.40	$242.40
Purchase #3	$172.32	4.222%	$179.5954	$179.60	$179.60	$179.60
Purchase #4	$116.28	12.776%	$131.1359	$131.14	$131.15	$131.10
Purchase #5	$78.42	12.860%	$88.5048	$88.50	$88.50	$88.50
Purchase #6	$161.74	3.738%	$167.7858	$167.79	$167.80	$167.80
Purchase #7	$153.82	11.111%	$170.9109	$170.91	$170.90	$170.90
7 purchase totals =	$939.72		$1,014.2099	$1,014.21	$1,014.20	$1,014.20