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	$200.44	9.528%	$219.5379	$219.54	$219.55	$219.50
Purchase #2	$226.57	12.366%	$254.5876	$254.59	$254.60	$254.60
Purchase #3	$165.29	12.764%	$186.3876	$186.39	$186.40	$186.40
Purchase #4	$231.31	3.767%	$240.0234	$240.02	$240.00	$240.00
Purchase #5	$54.38	12.764%	$61.3211	$61.32	$61.30	$61.30
Purchase #6	$208.31	12.276%	$233.8821	$233.88	$233.90	$233.90
Purchase #7	$66.51	6.798%	$71.0313	$71.03	$71.05	$71.00
7 purchase totals =	$1,152.81		$1,266.7710	$1,266.77	$1,266.80	$1,266.70