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	$162.39	11.681%	$181.3588	$181.36	$181.35	$181.40
Purchase #2	$184.89	13.487%	$209.8261	$209.83	$209.85	$209.80
Purchase #3	$35.59	12.209%	$39.9352	$39.94	$39.95	$39.90
Purchase #4	$58.34	11.176%	$64.8601	$64.86	$64.85	$64.90
Purchase #5	$222.80	5.565%	$235.1988	$235.20	$235.20	$235.20
Purchase #6	$28.76	11.311%	$32.013	$32.01	$32.00	$32.00
Purchase #7	$215.72	13.750%	$245.3815	$245.38	$245.40	$245.40
7 purchase totals =	$908.49		$1,008.5735	$1,008.58	$1,008.60	$1,008.60