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	$187.83	6.232%	$199.5356	$199.54	$199.55	$199.50
Purchase #2	$145.53	12.754%	$164.0909	$164.09	$164.10	$164.10
Purchase #3	$158.95	3.394%	$164.3448	$164.34	$164.35	$164.30
Purchase #4	$90.94	7.828%	$98.0588	$98.06	$98.05	$98.10
Purchase #5	$118.36	7.672%	$127.4406	$127.44	$127.45	$127.40
Purchase #6	$160.30	11.715%	$179.0791	$179.08	$179.10	$179.10
Purchase #7	$236.71	11.204%	$263.231	$263.23	$263.25	$263.20
7 purchase totals =	$1,098.62		$1,195.7808	$1,195.78	$1,195.85	$1,195.70