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	$82.45	5.392%	$86.8957	$86.90	$86.90	$86.90
Purchase #2	$168.45	4.556%	$176.1246	$176.12	$176.10	$176.10
Purchase #3	$179.25	5.124%	$188.4348	$188.43	$188.45	$188.40
Purchase #4	$31.86	7.372%	$34.2087	$34.21	$34.20	$34.20
Purchase #5	$202.78	5.296%	$213.5192	$213.52	$213.50	$213.50
Purchase #6	$243.31	6.424%	$258.9402	$258.94	$258.95	$258.90
Purchase #7	$57.30	7.337%	$61.5041	$61.50	$61.50	$61.50
7 purchase totals =	$965.40		$1,019.6273	$1,019.62	$1,019.60	$1,019.50