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	$69.99	4.143%	$72.8897	$72.89	$72.90	$72.90
Purchase #2	$61.78	4.146%	$64.3414	$64.34	$64.35	$64.30
Purchase #3	$232.62	12.435%	$261.5463	$261.55	$261.55	$261.50
Purchase #4	$203.70	10.358%	$224.7992	$224.80	$224.80	$224.80
Purchase #5	$145.97	12.378%	$164.0382	$164.04	$164.05	$164.00
Purchase #6	$82.32	8.298%	$89.1509	$89.15	$89.15	$89.20
Purchase #7	$128.44	6.861%	$137.2523	$137.25	$137.25	$137.30
7 purchase totals =	$924.82		$1,014.0180	$1,014.02	$1,014.05	$1,014.00