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	$159.74	13.189%	$180.8081	$180.81	$180.80	$180.80
Purchase #2	$23.77	7.408%	$25.5309	$25.53	$25.55	$25.50
Purchase #3	$73.82	13.549%	$83.8219	$83.82	$83.80	$83.80
Purchase #4	$132.31	10.587%	$146.3177	$146.32	$146.30	$146.30
Purchase #5	$61.56	9.274%	$67.2691	$67.27	$67.25	$67.30
Purchase #6	$89.81	7.195%	$96.2718	$96.27	$96.25	$96.30
Purchase #7	$126.81	3.336%	$131.0404	$131.04	$131.05	$131.00
7 purchase totals =	$667.82		$731.0599	$731.06	$731.00	$731.00