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	$118.69	10.517%	$131.1726	$131.17	$131.15	$131.20
Purchase #2	$162.34	3.774%	$168.4667	$168.47	$168.45	$168.50
Purchase #3	$155.50	8.338%	$168.4656	$168.47	$168.45	$168.50
Purchase #4	$142.50	9.616%	$156.2028	$156.20	$156.20	$156.20
Purchase #5	$43.62	11.207%	$48.5085	$48.51	$48.50	$48.50
Purchase #6	$193.43	4.645%	$202.4148	$202.41	$202.40	$202.40
Purchase #7	$124.71	10.560%	$137.8794	$137.88	$137.90	$137.90
7 purchase totals =	$940.79		$1,013.1104	$1,013.11	$1,013.05	$1,013.20