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	$219.37	13.373%	$248.7064	$248.71	$248.70	$248.70
Purchase #2	$226.61	7.375%	$243.3225	$243.32	$243.30	$243.30
Purchase #3	$210.94	10.546%	$233.1857	$233.19	$233.20	$233.20
Purchase #4	$21.56	12.417%	$24.2371	$24.24	$24.25	$24.20
Purchase #5	$146.93	3.334%	$151.8286	$151.83	$151.85	$151.80
Purchase #6	$118.83	7.623%	$127.8884	$127.89	$127.90	$127.90
Purchase #7	$181.44	9.620%	$198.8945	$198.89	$198.90	$198.90
7 purchase totals =	$1,125.68		$1,228.0632	$1,228.07	$1,228.10	$1,228.00