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	$113.98	12.133%	$127.8092	$127.81	$127.80	$127.80
Purchase #2	$9.67	12.129%	$10.8429	$10.84	$10.85	$10.80
Purchase #3	$168.50	3.512%	$174.4177	$174.42	$174.40	$174.40
Purchase #4	$146.38	12.270%	$164.3408	$164.34	$164.35	$164.30
Purchase #5	$117.49	8.475%	$127.4473	$127.45	$127.45	$127.40
Purchase #6	$51.83	12.644%	$58.3834	$58.38	$58.40	$58.40
Purchase #7	$76.82	8.235%	$83.1461	$83.15	$83.15	$83.10
7 purchase totals =	$684.67		$746.3874	$746.39	$746.40	$746.20