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	$89.95	12.845%	$101.5041	$101.50	$101.50	$101.50
Purchase #2	$22.31	3.829%	$23.1642	$23.16	$23.15	$23.20
Purchase #3	$39.84	13.453%	$45.1997	$45.20	$45.20	$45.20
Purchase #4	$173.94	3.600%	$180.2018	$180.20	$180.20	$180.20
Purchase #5	$146.51	12.193%	$164.374	$164.37	$164.35	$164.40
Purchase #6	$51.54	7.328%	$55.3169	$55.32	$55.30	$55.30
Purchase #7	$85.71	9.789%	$94.1002	$94.10	$94.10	$94.10
7 purchase totals =	$609.80		$663.8609	$663.85	$663.80	$663.90