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	$213.86	8.671%	$232.4038	$232.40	$232.40	$232.40
Purchase #2	$149.68	11.106%	$166.3035	$166.30	$166.30	$166.30
Purchase #3	$59.39	7.681%	$63.9517	$63.95	$63.95	$64.00
Purchase #4	$85.86	4.132%	$89.4077	$89.41	$89.40	$89.40
Purchase #5	$29.83	8.152%	$32.2617	$32.26	$32.25	$32.30
Purchase #6	$175.69	7.189%	$188.3204	$188.32	$188.30	$188.30
Purchase #7	$202.85	13.796%	$230.8352	$230.84	$230.85	$230.80
7 purchase totals =	$917.16		$1,003.4840	$1,003.48	$1,003.45	$1,003.50