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	$202.83	9.454%	$222.0055	$222.01	$222.00	$222.00
Purchase #2	$113.40	4.422%	$118.4145	$118.41	$118.40	$118.40
Purchase #3	$39.43	3.561%	$40.8341	$40.83	$40.85	$40.80
Purchase #4	$121.25	11.688%	$135.4217	$135.42	$135.40	$135.40
Purchase #5	$131.45	3.321%	$135.8155	$135.82	$135.80	$135.80
Purchase #6	$35.42	4.589%	$37.0454	$37.05	$37.05	$37.00
Purchase #7	$116.53	9.382%	$127.4628	$127.46	$127.45	$127.50
7 purchase totals =	$760.31		$816.9995	$817.00	$816.95	$816.90