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	$86.45	7.109%	$92.5957	$92.60	$92.60	$92.60
Purchase #2	$131.59	13.483%	$149.3323	$149.33	$149.35	$149.30
Purchase #3	$40.37	12.208%	$45.2984	$45.30	$45.30	$45.30
Purchase #4	$173.85	6.324%	$184.8443	$184.84	$184.85	$184.80
Purchase #5	$158.43	13.541%	$179.883	$179.88	$179.90	$179.90
Purchase #6	$242.99	7.519%	$261.2604	$261.26	$261.25	$261.30
Purchase #7	$63.54	13.456%	$72.0899	$72.09	$72.10	$72.10
7 purchase totals =	$897.22		$985.3040	$985.30	$985.35	$985.30