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	$149.36	12.107%	$167.443	$167.44	$167.45	$167.40
Purchase #2	$40.27	6.278%	$42.7982	$42.80	$42.80	$42.80
Purchase #3	$150.54	6.514%	$160.3462	$160.35	$160.35	$160.30
Purchase #4	$146.89	10.838%	$162.8099	$162.81	$162.80	$162.80
Purchase #5	$126.82	8.744%	$137.9091	$137.91	$137.90	$137.90
Purchase #6	$213.28	6.584%	$227.3224	$227.32	$227.30	$227.30
Purchase #7	$118.42	11.410%	$131.9317	$131.93	$131.95	$131.90
7 purchase totals =	$945.58		$1,030.5605	$1,030.56	$1,030.55	$1,030.40