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	$223.26	7.191%	$239.3146	$239.31	$239.30	$239.30
Purchase #2	$196.78	12.405%	$221.1906	$221.19	$221.20	$221.20
Purchase #3	$89.82	8.850%	$97.7691	$97.77	$97.75	$97.80
Purchase #4	$39.30	6.124%	$41.7067	$41.71	$41.70	$41.70
Purchase #5	$80.42	12.582%	$90.5384	$90.54	$90.55	$90.50
Purchase #6	$180.38	3.320%	$186.3686	$186.37	$186.35	$186.40
Purchase #7	$123.36	12.830%	$139.1871	$139.19	$139.20	$139.20
7 purchase totals =	$933.32		$1,016.0751	$1,016.08	$1,016.05	$1,016.10