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	$61.40	5.668%	$64.8802	$64.88	$64.90	$64.90
Purchase #2	$224.65	3.381%	$232.2454	$232.25	$232.25	$232.20
Purchase #3	$179.63	6.604%	$191.4928	$191.49	$191.50	$191.50
Purchase #4	$185.60	13.857%	$211.3186	$211.32	$211.30	$211.30
Purchase #5	$125.55	9.638%	$137.6505	$137.65	$137.65	$137.70
Purchase #6	$121.63	8.428%	$131.881	$131.88	$131.90	$131.90
Purchase #7	$184.96	6.186%	$196.4016	$196.40	$196.40	$196.40
7 purchase totals =	$1,083.42		$1,165.8701	$1,165.87	$1,165.90	$1,165.90