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	$140.31	3.570%	$145.3191	$145.32	$145.30	$145.30
Purchase #2	$156.25	13.203%	$176.8797	$176.88	$176.90	$176.90
Purchase #3	$130.77	11.696%	$146.0649	$146.06	$146.05	$146.10
Purchase #4	$39.28	9.136%	$42.8686	$42.87	$42.85	$42.90
Purchase #5	$231.26	3.308%	$238.9101	$238.91	$238.90	$238.90
Purchase #6	$226.59	9.715%	$248.6032	$248.60	$248.60	$248.60
Purchase #7	$234.76	3.442%	$242.8404	$242.84	$242.85	$242.80
7 purchase totals =	$1,159.22		$1,241.4860	$1,241.48	$1,241.45	$1,241.50