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	$126.25	3.799%	$131.0462	$131.05	$131.05	$131.00
Purchase #2	$97.32	6.745%	$103.8842	$103.88	$103.90	$103.90
Purchase #3	$231.35	8.541%	$251.1096	$251.11	$251.10	$251.10
Purchase #4	$102.51	3.193%	$105.7831	$105.78	$105.80	$105.80
Purchase #5	$222.33	8.640%	$241.5393	$241.54	$241.55	$241.50
Purchase #6	$127.72	10.529%	$141.1676	$141.17	$141.15	$141.20
Purchase #7	$140.54	4.526%	$146.9008	$146.90	$146.90	$146.90
7 purchase totals =	$1,048.02		$1,121.4308	$1,121.43	$1,121.45	$1,121.40