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	$146.83	10.488%	$162.2295	$162.23	$162.25	$162.20
Purchase #2	$65.91	8.155%	$71.285	$71.29	$71.30	$71.30
Purchase #3	$114.54	5.326%	$120.6404	$120.64	$120.65	$120.60
Purchase #4	$118.67	7.223%	$127.2415	$127.24	$127.25	$127.20
Purchase #5	$70.55	8.715%	$76.6984	$76.70	$76.70	$76.70
Purchase #6	$236.83	4.846%	$248.3068	$248.31	$248.30	$248.30
Purchase #7	$33.91	12.238%	$38.0599	$38.06	$38.05	$38.10
7 purchase totals =	$787.24		$844.4615	$844.47	$844.50	$844.40