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	$45.71	13.608%	$51.9302	$51.93	$51.95	$51.90
Purchase #2	$151.49	13.865%	$172.4941	$172.49	$172.50	$172.50
Purchase #3	$73.37	9.620%	$80.4282	$80.43	$80.45	$80.40
Purchase #4	$114.43	5.726%	$120.9823	$120.98	$121.00	$121.00
Purchase #5	$226.75	7.398%	$243.525	$243.53	$243.55	$243.50
Purchase #6	$233.96	9.602%	$256.4248	$256.42	$256.40	$256.40
Purchase #7	$66.35	7.391%	$71.2539	$71.25	$71.25	$71.30
7 purchase totals =	$912.06		$997.0385	$997.03	$997.10	$997.00