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	$38.31	5.304%	$40.342	$40.34	$40.35	$40.30
Purchase #2	$46.48	12.838%	$52.4471	$52.45	$52.45	$52.40
Purchase #3	$243.85	4.190%	$254.0673	$254.07	$254.05	$254.10
Purchase #4	$163.93	10.450%	$181.0607	$181.06	$181.05	$181.10
Purchase #5	$72.38	6.324%	$76.9573	$76.96	$76.95	$77.00
Purchase #6	$28.78	10.874%	$31.9095	$31.91	$31.90	$31.90
Purchase #7	$173.83	12.873%	$196.2071	$196.21	$196.20	$196.20
7 purchase totals =	$767.56		$832.9910	$833.00	$832.95	$833.00