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	$112.65	12.112%	$126.2942	$126.29	$126.30	$126.30
Purchase #2	$150.79	3.831%	$156.5668	$156.57	$156.55	$156.60
Purchase #3	$237.36	8.239%	$256.9161	$256.92	$256.90	$256.90
Purchase #4	$44.55	3.338%	$46.0371	$46.04	$46.05	$46.00
Purchase #5	$237.48	13.299%	$269.0625	$269.06	$269.05	$269.10
Purchase #6	$115.72	13.469%	$131.3063	$131.31	$131.30	$131.30
Purchase #7	$142.56	9.171%	$155.6342	$155.63	$155.65	$155.60
7 purchase totals =	$1,041.11		$1,141.8172	$1,141.82	$1,141.80	$1,141.80