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	$179.46	9.617%	$196.7187	$196.72	$196.70	$196.70
Purchase #2	$176.84	8.632%	$192.1048	$192.10	$192.10	$192.10
Purchase #3	$54.34	12.267%	$61.0059	$61.01	$61.00	$61.00
Purchase #4	$124.46	12.349%	$139.8296	$139.83	$139.85	$139.80
Purchase #5	$62.90	13.341%	$71.2915	$71.29	$71.30	$71.30
Purchase #6	$109.58	12.524%	$123.3038	$123.30	$123.30	$123.30
Purchase #7	$49.63	5.397%	$52.3085	$52.31	$52.30	$52.30
7 purchase totals =	$757.21		$836.5628	$836.56	$836.55	$836.50