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	$91.43	3.141%	$94.3018	$94.30	$94.30	$94.30
Purchase #2	$50.25	7.502%	$54.0198	$54.02	$54.00	$54.00
Purchase #3	$127.40	3.166%	$131.4335	$131.43	$131.45	$131.40
Purchase #4	$30.96	9.809%	$33.9969	$34.00	$34.00	$34.00
Purchase #5	$138.37	4.749%	$144.9412	$144.94	$144.95	$144.90
Purchase #6	$123.32	13.706%	$140.2222	$140.22	$140.20	$140.20
Purchase #7	$107.40	6.749%	$114.6484	$114.65	$114.65	$114.60
7 purchase totals =	$669.13		$713.5638	$713.56	$713.55	$713.40