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	$36.97	12.326%	$41.5269	$41.53	$41.55	$41.50
Purchase #2	$83.66	8.579%	$90.8372	$90.84	$90.85	$90.80
Purchase #3	$78.50	5.581%	$82.8811	$82.88	$82.90	$82.90
Purchase #4	$13.66	8.817%	$14.8644	$14.86	$14.85	$14.90
Purchase #5	$146.33	5.443%	$154.2947	$154.29	$154.30	$154.30
Purchase #6	$229.51	12.692%	$258.6394	$258.64	$258.65	$258.60
Purchase #7	$74.70	10.476%	$82.5256	$82.53	$82.55	$82.50
7 purchase totals =	$663.33		$725.5693	$725.57	$725.65	$725.50