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	$166.95	8.605%	$181.316	$181.32	$181.30	$181.30
Purchase #2	$250.65	9.499%	$274.4592	$274.46	$274.45	$274.50
Purchase #3	$95.84	5.556%	$101.1649	$101.16	$101.15	$101.20
Purchase #4	$71.92	8.845%	$78.2813	$78.28	$78.30	$78.30
Purchase #5	$208.35	7.209%	$223.37	$223.37	$223.35	$223.40
Purchase #6	$176.70	12.377%	$198.5702	$198.57	$198.55	$198.60
Purchase #7	$37.63	6.829%	$40.1998	$40.20	$40.20	$40.20
7 purchase totals =	$1,008.04		$1,097.3614	$1,097.36	$1,097.30	$1,097.50