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	$204.90	9.341%	$224.0397	$224.04	$224.05	$224.00
Purchase #2	$171.33	5.651%	$181.0119	$181.01	$181.00	$181.00
Purchase #3	$96.84	12.559%	$109.0021	$109.00	$109.00	$109.00
Purchase #4	$94.83	6.325%	$100.828	$100.83	$100.85	$100.80
Purchase #5	$89.92	10.462%	$99.3274	$99.33	$99.35	$99.30
Purchase #6	$160.72	12.188%	$180.3086	$180.31	$180.30	$180.30
Purchase #7	$77.30	10.188%	$85.1753	$85.18	$85.20	$85.20
7 purchase totals =	$895.84		$979.6930	$979.70	$979.75	$979.60