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	$142.75	7.230%	$153.0708	$153.07	$153.05	$153.10
Purchase #2	$146.25	6.847%	$156.2637	$156.26	$156.25	$156.30
Purchase #3	$65.77	9.358%	$71.9248	$71.92	$71.90	$71.90
Purchase #4	$63.86	13.284%	$72.3432	$72.34	$72.35	$72.30
Purchase #5	$138.54	12.792%	$156.262	$156.26	$156.25	$156.30
Purchase #6	$140.89	11.617%	$157.2572	$157.26	$157.25	$157.30
Purchase #7	$69.58	6.216%	$73.9051	$73.91	$73.90	$73.90
7 purchase totals =	$767.64		$841.0268	$841.02	$840.95	$841.10