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	$167.83	7.591%	$180.57	$180.57	$180.55	$180.60
Purchase #2	$211.48	9.601%	$231.7842	$231.78	$231.80	$231.80
Purchase #3	$250.71	7.300%	$269.0118	$269.01	$269.00	$269.00
Purchase #4	$164.98	13.308%	$186.9355	$186.94	$186.95	$186.90
Purchase #5	$40.42	11.663%	$45.1342	$45.13	$45.15	$45.10
Purchase #6	$247.48	8.471%	$268.444	$268.44	$268.45	$268.40
Purchase #7	$191.89	13.320%	$217.4497	$217.45	$217.45	$217.40
7 purchase totals =	$1,274.79		$1,399.3294	$1,399.32	$1,399.35	$1,399.20