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	$157.85	4.830%	$165.4742	$165.47	$165.45	$165.50
Purchase #2	$142.53	5.511%	$150.3848	$150.38	$150.40	$150.40
Purchase #3	$154.75	6.345%	$164.5689	$164.57	$164.55	$164.60
Purchase #4	$60.37	5.138%	$63.4718	$63.47	$63.45	$63.50
Purchase #5	$134.30	4.204%	$139.946	$139.95	$139.95	$139.90
Purchase #6	$76.48	12.225%	$85.8297	$85.83	$85.85	$85.80
Purchase #7	$243.26	3.527%	$251.8398	$251.84	$251.85	$251.80
7 purchase totals =	$969.54		$1,021.5152	$1,021.51	$1,021.50	$1,021.50