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	$218.29	13.703%	$248.2023	$248.20	$248.20	$248.20
Purchase #2	$81.59	9.778%	$89.5679	$89.57	$89.55	$89.60
Purchase #3	$244.98	10.778%	$271.3839	$271.38	$271.40	$271.40
Purchase #4	$93.81	5.426%	$98.9001	$98.90	$98.90	$98.90
Purchase #5	$55.54	3.336%	$57.3928	$57.39	$57.40	$57.40
Purchase #6	$179.50	3.623%	$186.0033	$186.00	$186.00	$186.00
Purchase #7	$10.78	7.578%	$11.5969	$11.60	$11.60	$11.60
7 purchase totals =	$884.49		$963.0472	$963.04	$963.05	$963.10