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	$55.64	12.174%	$62.4136	$62.41	$62.40	$62.40
Purchase #2	$143.43	7.719%	$154.5014	$154.50	$154.50	$154.50
Purchase #3	$64.37	11.542%	$71.7996	$71.80	$71.80	$71.80
Purchase #4	$124.62	7.720%	$134.2407	$134.24	$134.25	$134.20
Purchase #5	$85.51	3.184%	$88.2326	$88.23	$88.25	$88.20
Purchase #6	$142.85	10.747%	$158.2021	$158.20	$158.20	$158.20
Purchase #7	$90.36	10.752%	$100.0755	$100.08	$100.10	$100.10
7 purchase totals =	$706.78		$769.4655	$769.46	$769.50	$769.40