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	$118.78	6.157%	$126.0933	$126.09	$126.10	$126.10
Purchase #2	$238.43	9.547%	$261.1929	$261.19	$261.20	$261.20
Purchase #3	$147.85	3.424%	$152.9124	$152.91	$152.90	$152.90
Purchase #4	$97.34	3.199%	$100.4539	$100.45	$100.45	$100.50
Purchase #5	$134.72	13.495%	$152.9005	$152.90	$152.90	$152.90
Purchase #6	$31.50	8.311%	$34.118	$34.12	$34.10	$34.10
Purchase #7	$96.55	13.759%	$109.8343	$109.83	$109.85	$109.80
7 purchase totals =	$865.17		$937.5053	$937.49	$937.50	$937.50