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	$192.86	10.868%	$213.82	$213.82	$213.80	$213.80
Purchase #2	$22.26	13.783%	$25.3281	$25.33	$25.35	$25.30
Purchase #3	$86.64	13.257%	$98.1259	$98.13	$98.15	$98.10
Purchase #4	$117.63	8.670%	$127.8285	$127.83	$127.85	$127.80
Purchase #5	$118.71	10.616%	$131.3123	$131.31	$131.30	$131.30
Purchase #6	$179.78	4.686%	$188.2045	$188.20	$188.20	$188.20
Purchase #7	$67.69	5.556%	$71.4509	$71.45	$71.45	$71.50
7 purchase totals =	$785.57		$856.0702	$856.07	$856.10	$856.00