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	$118.70	7.479%	$127.5776	$127.58	$127.60	$127.60
Purchase #2	$224.29	4.386%	$234.1274	$234.13	$234.15	$234.10
Purchase #3	$121.65	4.276%	$126.8518	$126.85	$126.85	$126.90
Purchase #4	$173.39	13.361%	$196.5566	$196.56	$196.55	$196.60
Purchase #5	$158.26	4.675%	$165.6587	$165.66	$165.65	$165.70
Purchase #6	$137.53	8.369%	$149.0399	$149.04	$149.05	$149.00
Purchase #7	$248.35	12.757%	$280.032	$280.03	$280.05	$280.00
7 purchase totals =	$1,182.17		$1,279.8440	$1,279.85	$1,279.90	$1,279.90