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	$39.29	5.867%	$41.5951	$41.60	$41.60	$41.60
Purchase #2	$240.47	11.115%	$267.1982	$267.20	$267.20	$267.20
Purchase #3	$233.25	4.726%	$244.2734	$244.27	$244.25	$244.30
Purchase #4	$114.30	11.421%	$127.3542	$127.35	$127.35	$127.40
Purchase #5	$169.74	9.620%	$186.069	$186.07	$186.05	$186.10
Purchase #6	$229.56	11.328%	$255.5646	$255.56	$255.55	$255.60
Purchase #7	$137.46	7.350%	$147.5633	$147.56	$147.55	$147.60
7 purchase totals =	$1,164.07		$1,269.6178	$1,269.61	$1,269.55	$1,269.80