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	$218.70	13.359%	$247.9161	$247.92	$247.90	$247.90
Purchase #2	$93.47	12.619%	$105.265	$105.27	$105.25	$105.30
Purchase #3	$12.90	3.500%	$13.3515	$13.35	$13.35	$13.40
Purchase #4	$182.51	3.501%	$188.8997	$188.90	$188.90	$188.90
Purchase #5	$211.79	13.549%	$240.4854	$240.49	$240.50	$240.50
Purchase #6	$127.80	3.657%	$132.4736	$132.47	$132.45	$132.50
Purchase #7	$82.34	5.112%	$86.5492	$86.55	$86.55	$86.50
7 purchase totals =	$929.51		$1,014.9405	$1,014.95	$1,014.90	$1,015.00