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	$228.92	6.407%	$243.5869	$243.59	$243.60	$243.60
Purchase #2	$55.61	7.133%	$59.5767	$59.58	$59.60	$59.60
Purchase #3	$84.67	3.491%	$87.6258	$87.63	$87.65	$87.60
Purchase #4	$156.82	11.108%	$174.2396	$174.24	$174.25	$174.20
Purchase #5	$72.93	10.437%	$80.5417	$80.54	$80.55	$80.50
Purchase #6	$234.38	9.250%	$256.0602	$256.06	$256.05	$256.10
Purchase #7	$63.78	3.831%	$66.2234	$66.22	$66.20	$66.20
7 purchase totals =	$897.11		$967.8543	$967.86	$967.90	$967.80