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	$97.45	3.788%	$101.1414	$101.14	$101.15	$101.10
Purchase #2	$172.68	9.814%	$189.6268	$189.63	$189.65	$189.60
Purchase #3	$208.32	7.123%	$223.1586	$223.16	$223.15	$223.20
Purchase #4	$67.25	10.624%	$74.3946	$74.39	$74.40	$74.40
Purchase #5	$82.47	8.123%	$89.169	$89.17	$89.15	$89.20
Purchase #6	$174.27	4.808%	$182.6489	$182.65	$182.65	$182.60
Purchase #7	$228.55	9.853%	$251.069	$251.07	$251.05	$251.10
7 purchase totals =	$1,030.99		$1,111.2083	$1,111.21	$1,111.20	$1,111.20