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	$28.64	9.717%	$31.4229	$31.42	$31.40	$31.40
Purchase #2	$123.37	3.239%	$127.366	$127.37	$127.35	$127.40
Purchase #3	$169.53	13.505%	$192.425	$192.43	$192.45	$192.40
Purchase #4	$220.74	13.652%	$250.8754	$250.88	$250.90	$250.90
Purchase #5	$85.84	7.549%	$92.3201	$92.32	$92.30	$92.30
Purchase #6	$143.76	12.811%	$162.1771	$162.18	$162.20	$162.20
Purchase #7	$172.94	9.208%	$188.8643	$188.86	$188.85	$188.90
7 purchase totals =	$944.82		$1,045.4508	$1,045.46	$1,045.45	$1,045.50