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	$12.64	9.400%	$13.8282	$13.83	$13.85	$13.80
Purchase #2	$196.49	5.112%	$206.5346	$206.53	$206.55	$206.50
Purchase #3	$239.96	9.200%	$262.0363	$262.04	$262.05	$262.00
Purchase #4	$6.29	9.208%	$6.8692	$6.87	$6.85	$6.90
Purchase #5	$191.57	4.477%	$200.1466	$200.15	$200.15	$200.10
Purchase #6	$179.94	10.506%	$198.8445	$198.84	$198.85	$198.80
Purchase #7	$40.69	12.165%	$45.6399	$45.64	$45.65	$45.60
7 purchase totals =	$867.58		$933.8993	$933.90	$933.95	$933.70