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	$189.90	3.328%	$196.2199	$196.22	$196.20	$196.20
Purchase #2	$241.51	12.268%	$271.1384	$271.14	$271.15	$271.10
Purchase #3	$146.95	13.588%	$166.9176	$166.92	$166.90	$166.90
Purchase #4	$164.71	10.436%	$181.8991	$181.90	$181.90	$181.90
Purchase #5	$215.57	12.551%	$242.6262	$242.63	$242.65	$242.60
Purchase #6	$13.39	7.570%	$14.4036	$14.40	$14.40	$14.40
Purchase #7	$18.57	9.102%	$20.2602	$20.26	$20.25	$20.30
7 purchase totals =	$990.60		$1,093.4650	$1,093.47	$1,093.45	$1,093.40