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	$243.25	5.444%	$256.4925	$256.49	$256.50	$256.50
Purchase #2	$108.72	7.507%	$116.8816	$116.88	$116.90	$116.90
Purchase #3	$79.84	13.565%	$90.6703	$90.67	$90.65	$90.70
Purchase #4	$200.31	11.183%	$222.7107	$222.71	$222.70	$222.70
Purchase #5	$148.84	4.822%	$156.0171	$156.02	$156.00	$156.00
Purchase #6	$87.50	8.221%	$94.6934	$94.69	$94.70	$94.70
Purchase #7	$68.32	12.484%	$76.8491	$76.85	$76.85	$76.80
7 purchase totals =	$936.78		$1,014.3147	$1,014.31	$1,014.30	$1,014.30