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	$113.92	8.385%	$123.4722	$123.47	$123.45	$123.50
Purchase #2	$21.27	7.616%	$22.8899	$22.89	$22.90	$22.90
Purchase #3	$208.71	8.237%	$225.9014	$225.90	$225.90	$225.90
Purchase #4	$176.43	11.293%	$196.3542	$196.35	$196.35	$196.40
Purchase #5	$218.37	6.801%	$233.2213	$233.22	$233.20	$233.20
Purchase #6	$63.69	9.455%	$69.7119	$69.71	$69.70	$69.70
Purchase #7	$232.88	3.286%	$240.5324	$240.53	$240.55	$240.50
7 purchase totals =	$1,035.27		$1,112.0833	$1,112.07	$1,112.05	$1,112.10