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	$113.39	9.307%	$123.9432	$123.94	$123.95	$123.90
Purchase #2	$226.50	7.245%	$242.9099	$242.91	$242.90	$242.90
Purchase #3	$147.77	9.354%	$161.5924	$161.59	$161.60	$161.60
Purchase #4	$91.39	8.127%	$98.8173	$98.82	$98.80	$98.80
Purchase #5	$203.50	9.450%	$222.7308	$222.73	$222.75	$222.70
Purchase #6	$150.71	9.361%	$164.818	$164.82	$164.80	$164.80
Purchase #7	$232.51	11.588%	$259.4533	$259.45	$259.45	$259.50
7 purchase totals =	$1,165.77		$1,274.2649	$1,274.26	$1,274.25	$1,274.20